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Parabola

Mathematics · FE Reference Handbook section

Mathematics
2 formulas
10 exam-style examples
~49 min
All Mathematics lectures

Core formulas for this FE topic

Definitions, applicability, units, assumptions and worked examples for each relation.

Worked exam-style examples

The four ways this section is written on the real exam — thoughts first, then equations, then substitution.

Example 1
Parabola vertex form — solve for y-value — Parabola

A mathematics problem uses Parabola vertex form. Given coefficient (a) = 0.6000; x-value (x) = 0.0000; vertex x (h) = -3.0000; vertex y (k) = 1.0000, determine the y-value (y).

Given

  • coefficient(a)=0.6000coefficient (a) = 0.6000
  • x−value(x)=0.0000x-value (x) = 0.0000
  • vertexx(h)=−3.0000vertex x (h) = -3.0000
  • vertexy(k)=1.0000vertex y (k) = 1.0000

Find

y-value (y)

Start with the thinking

  • The governing relation printed in this handbook section is Parabola vertex form.
  • Everything except y is given, so isolate y symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Mathematics items reward recognising the unknown before touching a calculator.

Step-by-step solution

  1. Step 1 — State the governing relation:

    y=a(x−h)2+ky = a (x - h)^2 + k
  2. Step 2 — Rearrange the relation so that y stands alone on the left-hand side.

  3. Step 3

    Listthegivens:coefficient(a)=0.6000,x−value(x)=0.0000,vertexx(h)=−3.0000,vertexy(k)=1.0000List the givens: coefficient (a) = 0.6000, x-value (x) = 0.0000, vertex x (h) = -3.0000, vertex y (k) = 1.0000
  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    y=6.4000y = 6.4000
  6. Step 6 — Check: returning y = 6.4000 to

    y=a(x−h)2+ky = a (x - h)^2 + k

    reproduces the given quantities, and both sides carry the same units.

Answer:
y=6.4000y = 6.4000

Why the other options are there

  • 12.8000 — kept a factor of two that cancels in the correct rearrangement.
  • 3.2000 — dropped that same factor in the other direction.
  • 7.0400 — rounded an intermediate value before the final step.

Reference: FE Reference Handbook — Mathematics → Parabola

Example 2
Parabola (vertex form) — solve for elevation — Parabola (2)

A vertical curve profile is modeled as a parabola. Given curvature coefficient (a) = 0.2000 1/m; station offset (x) = 28.5000 m; vertex station (h) = 1.1000 m; vertex elevation (k) = 8.8000 m, determine the elevation (y) in m.

Given

  • curvaturecoefficient(a)=0.20001/mcurvature coefficient (a) = 0.2000 1/m
  • stationoffset(x)=28.5000mstation offset (x) = 28.5000 m
  • vertexstation(h)=1.1000mvertex station (h) = 1.1000 m
  • vertexelevation(k)=8.8000mvertex elevation (k) = 8.8000 m

Find

elevation (y), in m

Start with the thinking

  • The governing relation printed in this handbook section is Parabola (vertex form).
  • Everything except y is given, so isolate y symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • A vertical curve profile is modeled as a parabola.

Step-by-step solution

  1. Step 1 — State the governing relation:

    y=a(x−h)2+ky = a(x - h)^2 + k
  2. Step 2 — Rearrange symbolically for y:

    y=y=a(x−h)2+ky = y = a(x - h)^2 + k
  3. Step 3 — List the givens: curvature coefficient (a) = 0.2000 1/m, station offset (x) = 28.5000 m, vertex station (h) = 1.1000 m, vertex elevation (k) = 8.8000 m.

  4. Step 4 — Substitute the given values:

    y=y=0.2000(28.5000−1.1000)2+8.8000y = y = 0.2000(28.5000 - 1.1000)^2 + 8.8000
  5. Step 5 — Evaluate:

    y=159.0 my = 159.0\ \text{m}
  6. Step 6 — Check: returning y = 159.0 m to

    y=a(x−h)2+ky = a(x - h)^2 + k

    reproduces the given quantities, and both sides carry the same units.

Answer:
y=159.0 my = 159.0\ \text{m}

Why the other options are there

  • 317.9 — kept a factor of two that cancels in the correct rearrangement.
  • 79.4760 — dropped that same factor in the other direction.
  • 174.8 — rounded an intermediate value before the final step.

Reference: FE Handbook — Conic Sections (Parabola)

Example 3
Parabola vertex form — solve for coefficient — Parabola (3)

A mathematics problem uses Parabola vertex form. Given x-value (x) = -3.0000; vertex x (h) = -2.5000; vertex y (k) = 2.5000; y-value (y) = 11.2000, determine the coefficient (a).

Given

  • x−value(x)=−3.0000x-value (x) = -3.0000
  • vertexx(h)=−2.5000vertex x (h) = -2.5000
  • vertexy(k)=2.5000vertex y (k) = 2.5000
  • y−value(y)=11.2000y-value (y) = 11.2000

Find

coefficient (a)

Start with the thinking

  • The governing relation printed in this handbook section is Parabola vertex form.
  • Everything except a is given, so isolate a symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Mathematics items reward recognising the unknown before touching a calculator.

Step-by-step solution

  1. Step 1 — State the governing relation:

    y=a(x−h)2+ky = a (x - h)^2 + k
  2. Step 2 — Rearrange the relation so that a stands alone on the left-hand side.

  3. Step 3

    Listthegivens:x−value(x)=−3.0000,vertexx(h)=−2.5000,vertexy(k)=2.5000,y−value(y)=11.2000List the givens: x-value (x) = -3.0000, vertex x (h) = -2.5000, vertex y (k) = 2.5000, y-value (y) = 11.2000
  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    a=34.8000a = 34.8000
  6. Step 6 — Check: returning a = 34.8000 to

    y=a(x−h)2+ky = a (x - h)^2 + k

    reproduces the given quantities, and both sides carry the same units.

Answer:
a=34.8000a = 34.8000

Why the other options are there

  • 69.6000 — kept a factor of two that cancels in the correct rearrangement.
  • 17.4000 — dropped that same factor in the other direction.
  • 38.2800 — rounded an intermediate value before the final step.

Reference: FE Reference Handbook — Mathematics → Parabola

Example 4
Parabola (vertex form) — solve for curvature coefficient — Parabola (4)

A vertical curve profile is modeled as a parabola. Given elevation (y) = 12.5000 m; station offset (x) = 27.5000 m; vertex station (h) = 6.1000 m; vertex elevation (k) = 9.9000 m, determine the curvature coefficient (a) in 1/m.

Given

  • elevation(y)=12.5000melevation (y) = 12.5000 m
  • stationoffset(x)=27.5000mstation offset (x) = 27.5000 m
  • vertexstation(h)=6.1000mvertex station (h) = 6.1000 m
  • vertexelevation(k)=9.9000mvertex elevation (k) = 9.9000 m

Find

curvature coefficient (a), in 1/m

Start with the thinking

  • The governing relation printed in this handbook section is Parabola (vertex form).
  • Everything except a is given, so isolate a symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • A vertical curve profile is modeled as a parabola.

Step-by-step solution

  1. Step 1 — State the governing relation:

    y=a(x−h)2+ky = a(x - h)^2 + k
  2. Step 2 — Rearrange symbolically for a:

    a=a=y−k(x−h)2a = a = \dfrac{y - k}{(x - h)^2}
  3. Step 3 — List the givens: elevation (y) = 12.5000 m, station offset (x) = 27.5000 m, vertex station (h) = 6.1000 m, vertex elevation (k) = 9.9000 m.

  4. Step 4 — Substitute the given values:

    a=a=12.5000−9.9000(27.5000−6.1000)2a = a = \dfrac{12.5000 - 9.9000}{(27.5000 - 6.1000)^2}
  5. Step 5 — Evaluate:

    a=0.0057 1/ma = 0.0057\ \text{1/m}
  6. Step 6 — Check: returning a = 0.0057 1/m to

    y=a(x−h)2+ky = a(x - h)^2 + k

    reproduces the given quantities, and both sides carry the same units.

Answer:
a=0.0057 1/ma = 0.0057\ \text{1/m}

Why the other options are there

  • 0.0114 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0028 — dropped that same factor in the other direction.
  • 0.0062 — rounded an intermediate value before the final step.

Reference: FE Handbook — Conic Sections (Parabola)

Example 5
Parabola vertex form — solve for vertex y — Parabola (5)

A mathematics problem uses Parabola vertex form. Given coefficient (a) = 2.0000; x-value (x) = 2.5000; vertex x (h) = -1.5000; y-value (y) = -38.8000, determine the vertex y (k).

Given

  • coefficient(a)=2.0000coefficient (a) = 2.0000
  • x−value(x)=2.5000x-value (x) = 2.5000
  • vertexx(h)=−1.5000vertex x (h) = -1.5000
  • y−value(y)=−38.8000y-value (y) = -38.8000

Find

vertex y (k)

Start with the thinking

  • The governing relation printed in this handbook section is Parabola vertex form.
  • Everything except k is given, so isolate k symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Mathematics items reward recognising the unknown before touching a calculator.

Step-by-step solution

  1. Step 1 — State the governing relation:

    y=a(x−h)2+ky = a (x - h)^2 + k
  2. Step 2 — Rearrange the relation so that k stands alone on the left-hand side.

  3. Step 3 — List the givens: coefficient (a) = 2.0000, x-value (x) = 2.5000, vertex x (h) = -1.5000, y-value (y) = -38.8000.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    k=−70.8000k = -70.8000
  6. Step 6 — Check: returning k = -70.8000 to

    y=a(x−h)2+ky = a (x - h)^2 + k

    reproduces the given quantities, and both sides carry the same units.

Answer:
k=−70.8000k = -70.8000

Why the other options are there

  • -141.6 — kept a factor of two that cancels in the correct rearrangement.
  • -35.4000 — dropped that same factor in the other direction.
  • -77.8800 — rounded an intermediate value before the final step.

Reference: FE Reference Handbook — Mathematics → Parabola

Example 6
Parabola (vertex form) — solve for vertex elevation — Parabola (6)

A vertical curve profile is modeled as a parabola. Given elevation (y) = 12.8000 m; curvature coefficient (a) = 0.3000 1/m; station offset (x) = 8.4000 m; vertex station (h) = 8.2000 m, determine the vertex elevation (k) in m.

Given

  • elevation(y)=12.8000melevation (y) = 12.8000 m
  • curvaturecoefficient(a)=0.30001/mcurvature coefficient (a) = 0.3000 1/m
  • stationoffset(x)=8.4000mstation offset (x) = 8.4000 m
  • vertexstation(h)=8.2000mvertex station (h) = 8.2000 m

Find

vertex elevation (k), in m

Start with the thinking

  • The governing relation printed in this handbook section is Parabola (vertex form).
  • Everything except k is given, so isolate k symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • A vertical curve profile is modeled as a parabola.

Step-by-step solution

  1. Step 1 — State the governing relation:

    y=a(x−h)2+ky = a(x - h)^2 + k
  2. Step 2 — Rearrange symbolically for k:

    k=k=y−a(x−h)2k = k = y - a(x - h)^2
  3. Step 3 — List the givens: elevation (y) = 12.8000 m, curvature coefficient (a) = 0.3000 1/m, station offset (x) = 8.4000 m, vertex station (h) = 8.2000 m.

  4. Step 4 — Substitute the given values:

    k=k=12.8000−0.3000(8.4000−8.2000)2k = k = 12.8000 - 0.3000(8.4000 - 8.2000)^2
  5. Step 5 — Evaluate:

    k=12.7880 mk = 12.7880\ \text{m}
  6. Step 6 — Check: returning k = 12.7880 m to

    y=a(x−h)2+ky = a(x - h)^2 + k

    reproduces the given quantities, and both sides carry the same units.

Answer:
k=12.7880 mk = 12.7880\ \text{m}

Why the other options are there

  • 25.5760 — kept a factor of two that cancels in the correct rearrangement.
  • 6.3940 — dropped that same factor in the other direction.
  • 14.0668 — rounded an intermediate value before the final step.

Reference: FE Handbook — Conic Sections (Parabola)

Example 7
Parabola vertex form — solve for y-value (case 2) — Parabola (7)

A mathematics problem uses Parabola vertex form. Given coefficient (a) = 2.8000; x-value (x) = 4.0000; vertex x (h) = 1.5000; vertex y (k) = -1.0000, determine the y-value (y).

Given

  • coefficient(a)=2.8000coefficient (a) = 2.8000
  • x−value(x)=4.0000x-value (x) = 4.0000
  • vertexx(h)=1.5000vertex x (h) = 1.5000
  • vertexy(k)=−1.0000vertex y (k) = -1.0000

Find

y-value (y)

Start with the thinking

  • The governing relation printed in this handbook section is Parabola vertex form.
  • Everything except y is given, so isolate y symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Mathematics items reward recognising the unknown before touching a calculator.

Step-by-step solution

  1. Step 1 — State the governing relation:

    y=a(x−h)2+ky = a (x - h)^2 + k
  2. Step 2 — Rearrange the relation so that y stands alone on the left-hand side.

  3. Step 3

    Listthegivens:coefficient(a)=2.8000,x−value(x)=4.0000,vertexx(h)=1.5000,vertexy(k)=−1.0000List the givens: coefficient (a) = 2.8000, x-value (x) = 4.0000, vertex x (h) = 1.5000, vertex y (k) = -1.0000
  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    y=16.5000y = 16.5000
  6. Step 6 — Check: returning y = 16.5000 to

    y=a(x−h)2+ky = a (x - h)^2 + k

    reproduces the given quantities, and both sides carry the same units.

Answer:
y=16.5000y = 16.5000

Why the other options are there

  • 33.0000 — kept a factor of two that cancels in the correct rearrangement.
  • 8.2500 — dropped that same factor in the other direction.
  • 18.1500 — rounded an intermediate value before the final step.

Reference: FE Reference Handbook — Mathematics → Parabola

Example 8
Parabola (vertex form) — solve for elevation (case 2) — Parabola (8)

A vertical curve profile is modeled as a parabola. Given curvature coefficient (a) = 0.2000 1/m; station offset (x) = 17.5000 m; vertex station (h) = 1.3000 m; vertex elevation (k) = 12.3000 m, determine the elevation (y) in m.

Given

  • curvaturecoefficient(a)=0.20001/mcurvature coefficient (a) = 0.2000 1/m
  • stationoffset(x)=17.5000mstation offset (x) = 17.5000 m
  • vertexstation(h)=1.3000mvertex station (h) = 1.3000 m
  • vertexelevation(k)=12.3000mvertex elevation (k) = 12.3000 m

Find

elevation (y), in m

Start with the thinking

  • The governing relation printed in this handbook section is Parabola (vertex form).
  • Everything except y is given, so isolate y symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • A vertical curve profile is modeled as a parabola.

Step-by-step solution

  1. Step 1 — State the governing relation:

    y=a(x−h)2+ky = a(x - h)^2 + k
  2. Step 2 — Rearrange symbolically for y:

    y=y=a(x−h)2+ky = y = a(x - h)^2 + k
  3. Step 3 — List the givens: curvature coefficient (a) = 0.2000 1/m, station offset (x) = 17.5000 m, vertex station (h) = 1.3000 m, vertex elevation (k) = 12.3000 m.

  4. Step 4 — Substitute the given values:

    y=y=0.2000(17.5000−1.3000)2+12.3000y = y = 0.2000(17.5000 - 1.3000)^2 + 12.3000
  5. Step 5 — Evaluate:

    y=64.7880 my = 64.7880\ \text{m}
  6. Step 6 — Check: returning y = 64.7880 m to

    y=a(x−h)2+ky = a(x - h)^2 + k

    reproduces the given quantities, and both sides carry the same units.

Answer:
y=64.7880 my = 64.7880\ \text{m}

Why the other options are there

  • 129.6 — kept a factor of two that cancels in the correct rearrangement.
  • 32.3940 — dropped that same factor in the other direction.
  • 71.2668 — rounded an intermediate value before the final step.

Reference: FE Handbook — Conic Sections (Parabola)

Example 9
Parabola vertex form — solve for coefficient (case 2) — Parabola (9)

A mathematics problem uses Parabola vertex form. Given x-value (x) = 3.0000; vertex x (h) = 2.5000; vertex y (k) = 3.0000; y-value (y) = -17.1000, determine the coefficient (a).

Given

  • x−value(x)=3.0000x-value (x) = 3.0000
  • vertexx(h)=2.5000vertex x (h) = 2.5000
  • vertexy(k)=3.0000vertex y (k) = 3.0000
  • y−value(y)=−17.1000y-value (y) = -17.1000

Find

coefficient (a)

Start with the thinking

  • The governing relation printed in this handbook section is Parabola vertex form.
  • Everything except a is given, so isolate a symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Mathematics items reward recognising the unknown before touching a calculator.

Step-by-step solution

  1. Step 1 — State the governing relation:

    y=a(x−h)2+ky = a (x - h)^2 + k
  2. Step 2 — Rearrange the relation so that a stands alone on the left-hand side.

  3. Step 3

    Listthegivens:x−value(x)=3.0000,vertexx(h)=2.5000,vertexy(k)=3.0000,y−value(y)=−17.1000List the givens: x-value (x) = 3.0000, vertex x (h) = 2.5000, vertex y (k) = 3.0000, y-value (y) = -17.1000
  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    a=−80.4000a = -80.4000
  6. Step 6 — Check: returning a = -80.4000 to

    y=a(x−h)2+ky = a (x - h)^2 + k

    reproduces the given quantities, and both sides carry the same units.

Answer:
a=−80.4000a = -80.4000

Why the other options are there

  • -160.8 — kept a factor of two that cancels in the correct rearrangement.
  • -40.2000 — dropped that same factor in the other direction.
  • -88.4400 — rounded an intermediate value before the final step.

Reference: FE Reference Handbook — Mathematics → Parabola

Example 10
Parabola (vertex form) — solve for curvature coefficient (case 2) — Parabola (10)

A vertical curve profile is modeled as a parabola. Given elevation (y) = 32.8000 m; station offset (x) = 14.0000 m; vertex station (h) = 8.0000 m; vertex elevation (k) = 8.9000 m, determine the curvature coefficient (a) in 1/m.

Given

  • elevation(y)=32.8000melevation (y) = 32.8000 m
  • stationoffset(x)=14.0000mstation offset (x) = 14.0000 m
  • vertexstation(h)=8.0000mvertex station (h) = 8.0000 m
  • vertexelevation(k)=8.9000mvertex elevation (k) = 8.9000 m

Find

curvature coefficient (a), in 1/m

Start with the thinking

  • The governing relation printed in this handbook section is Parabola (vertex form).
  • Everything except a is given, so isolate a symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • A vertical curve profile is modeled as a parabola.

Step-by-step solution

  1. Step 1 — State the governing relation:

    y=a(x−h)2+ky = a(x - h)^2 + k
  2. Step 2 — Rearrange symbolically for a:

    a=a=y−k(x−h)2a = a = \dfrac{y - k}{(x - h)^2}
  3. Step 3 — List the givens: elevation (y) = 32.8000 m, station offset (x) = 14.0000 m, vertex station (h) = 8.0000 m, vertex elevation (k) = 8.9000 m.

  4. Step 4 — Substitute the given values:

    a=a=32.8000−8.9000(14.0000−8.0000)2a = a = \dfrac{32.8000 - 8.9000}{(14.0000 - 8.0000)^2}
  5. Step 5 — Evaluate:

    a=0.6639 1/ma = 0.6639\ \text{1/m}
  6. Step 6 — Check: returning a = 0.6639 1/m to

    y=a(x−h)2+ky = a(x - h)^2 + k

    reproduces the given quantities, and both sides carry the same units.

Answer:
a=0.6639 1/ma = 0.6639\ \text{1/m}

Why the other options are there

  • 1.3278 — kept a factor of two that cancels in the correct rearrangement.
  • 0.3319 — dropped that same factor in the other direction.
  • 0.7303 — rounded an intermediate value before the final step.

Reference: FE Handbook — Conic Sections (Parabola)

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