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Straight Line

Mathematics · FE Reference Handbook section

Mathematics
7 formulas
10 exam-style examples
~59 min
All Mathematics lectures

Handbook notes for this section

Definitions and conditions exactly as the handbook states them.

  • The general form of the equation is
  • The standard form of the equation is
  • which is also known as the slope-intercept form.
  • The angle between lines with slopes m1 and m2 is
  • The distance between two points is

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
Slope–intercept line — solve for y-value — Straight Line

A mathematics problem uses Slope–intercept line. Given slope (m) = 0.9000; x-value (x) = 5.5000; intercept (b) = -9.0000, determine the y-value (y).

Given

  • slope(m)=0.9000slope (m) = 0.9000
  • x−value(x)=5.5000x-value (x) = 5.5000
  • intercept(b)=−9.0000intercept (b) = -9.0000

Find

y-value (y)

Start with the thinking

  • The governing relation printed in this handbook section is Slope–intercept line.
  • 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=mx+by = m x + b
  2. Step 2 — Rearrange the relation so that y stands alone on the left-hand side.

  3. Step 3

    Listthegivens:slope(m)=0.9000,x−value(x)=5.5000,intercept(b)=−9.0000List the givens: slope (m) = 0.9000, x-value (x) = 5.5000, intercept (b) = -9.0000
  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    y=−4.0500y = -4.0500
  6. Step 6 — Check: returning y = -4.0500 to

    y=mx+by = m x + b

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

Answer:
y=−4.0500y = -4.0500

Why the other options are there

  • -8.1000 — kept a factor of two that cancels in the correct rearrangement.
  • -2.0250 — dropped that same factor in the other direction.
  • -4.4550 — rounded an intermediate value before the final step.

Reference: FE Reference Handbook — Mathematics → Straight Line

Example 2
Straight Line — two-point slope — solve for slope — Straight Line (2)

A designer checks the slope of a straight line on a site grading plan. Given x1 (x1) = 5.0000; x2 (x2) = 9.0000; y1 (y1) = 6.5000; y2 (y2) = 26.0000, determine the slope (m).

Given

  • x1(x1)=5.0000x_{1} (x_{1}) = 5.0000
  • x2(x2)=9.0000x_{2} (x_{2}) = 9.0000
  • y1(y1)=6.5000y_{1} (y_{1}) = 6.5000
  • y2(y2)=26.0000y_{2} (y_{2}) = 26.0000

Find

slope (m)

Start with the thinking

  • The governing relation printed in this handbook section is Straight Line — two-point slope.
  • Everything except m is given, so isolate m 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.
  • The FE Handbook Straight Line relation gives the slope through two points on a line.
(1, -3)(10, 12)xyStraight line through two points

Figure 2 — schematic for Straight Line — two-point slope — solve for slope — Straight Line (2)

Step-by-step solution

  1. Step 1 — State the governing relation:

    m=y2−y1x2−x1m = \dfrac{y_2 - y_1}{x_2 - x_1}
  2. Step 2 — Rearrange symbolically for m:

    m=y2−y1x2−x1m = \dfrac{y_2 - y_1}{x_2 - x_1}
  3. Step 3

    Listthegivens:x1(x1)=5.0000,x2(x2)=9.0000,y1(y1)=6.5000,y2(y2)=26.0000List the givens: x_{1} (x_{1}) = 5.0000, x_{2} (x_{2}) = 9.0000, y_{1} (y_{1}) = 6.5000, y_{2} (y_{2}) = 26.0000
  4. Step 4 — Substitute the given values:

    m=y2−y1x2−x1m = \dfrac{y_2 - y_1}{x_2 - x_1}
  5. Step 5 — Evaluate:

    m=4.8750m = 4.8750
  6. Step 6 — Check: returning m = 4.8750 to

    m=y2−y1x2−x1m = \dfrac{y_2 - y_1}{x_2 - x_1}

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

Answer:
m=4.8750m = 4.8750

Why the other options are there

  • 9.7500 — kept a factor of two that cancels in the correct rearrangement.
  • 2.4375 — dropped that same factor in the other direction.
  • 5.3625 — rounded an intermediate value before the final step.

Reference: FE Handbook — Straight Line

Example 3
Slope–intercept line — solve for slope — Straight Line (3)

A mathematics problem uses Slope–intercept line. Given x-value (x) = 8.0000; intercept (b) = 9.5000; y-value (y) = 54.4000, determine the slope (m).

Given

  • x−value(x)=8.0000x-value (x) = 8.0000
  • intercept(b)=9.5000intercept (b) = 9.5000
  • y−value(y)=54.4000y-value (y) = 54.4000

Find

slope (m)

Start with the thinking

  • The governing relation printed in this handbook section is Slope–intercept line.
  • Everything except m is given, so isolate m 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=mx+by = m x + b
  2. Step 2 — Rearrange the relation so that m stands alone on the left-hand side.

  3. Step 3

    Listthegivens:x−value(x)=8.0000,intercept(b)=9.5000,y−value(y)=54.4000List the givens: x-value (x) = 8.0000, intercept (b) = 9.5000, y-value (y) = 54.4000
  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    m=5.6125m = 5.6125
  6. Step 6 — Check: returning m = 5.6125 to

    y=mx+by = m x + b

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

Answer:
m=5.6125m = 5.6125

Why the other options are there

  • 11.2250 — kept a factor of two that cancels in the correct rearrangement.
  • 2.8063 — dropped that same factor in the other direction.
  • 6.1738 — rounded an intermediate value before the final step.

Reference: FE Reference Handbook — Mathematics → Straight Line

Example 4
Straight Line — two-point slope — solve for y2 — Straight Line (4)

A drafter verifies a straight line segment on a coordinate layout. Given x1 (x1) = 3.5000; x2 (x2) = 13.5000; y1 (y1) = 5.5000; slope (m) = 3.0500, determine the y2 (y2).

Given

  • x1(x1)=3.5000x_{1} (x_{1}) = 3.5000
  • x2(x2)=13.5000x_{2} (x_{2}) = 13.5000
  • y1(y1)=5.5000y_{1} (y_{1}) = 5.5000
  • slope(m)=3.0500slope (m) = 3.0500

Find

y2 (y2)

Start with the thinking

  • The governing relation printed in this handbook section is Straight Line — two-point slope.
  • Everything except y2 is given, so isolate y2 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.
  • The FE Handbook Straight Line relation gives the slope through two points on a line.
(1, -3)(10, 12)xyStraight line through two points

Figure 4 — schematic for Straight Line — two-point slope — solve for y2 — Straight Line (4)

Step-by-step solution

  1. Step 1 — State the governing relation:

    m=y2−y1x2−x1m = \dfrac{y_2 - y_1}{x_2 - x_1}
  2. Step 2 — Rearrange symbolically for y2:

    y2=m(x2−x1)+y1y_{2} = m (x_2 - x_1) + y_1
  3. Step 3

    Listthegivens:x1(x1)=3.5000,x2(x2)=13.5000,y1(y1)=5.5000,slope(m)=3.0500List the givens: x_{1} (x_{1}) = 3.5000, x_{2} (x_{2}) = 13.5000, y_{1} (y_{1}) = 5.5000, slope (m) = 3.0500
  4. Step 4 — Substitute the given values:

    y2=3.0500(x2−x1)+y1y_{2} = 3.0500 (x_2 - x_1) + y_1
  5. Step 5 — Evaluate:

    y2=36.0000y_{2} = 36.0000
  6. Step 6 — Check: returning y2 = 36.0000 to

    m=y2−y1x2−x1m = \dfrac{y_2 - y_1}{x_2 - x_1}

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

Answer:
y2=36.0000y_{2} = 36.0000

Why the other options are there

  • 72.0000 — kept a factor of two that cancels in the correct rearrangement.
  • 18.0000 — dropped that same factor in the other direction.
  • 39.6000 — rounded an intermediate value before the final step.

Reference: FE Handbook — Straight Line

Example 5
Slope–intercept line — solve for intercept — Straight Line (5)

A mathematics problem uses Slope–intercept line. Given slope (m) = 2.0000; x-value (x) = 7.0000; y-value (y) = 38.3000, determine the intercept (b).

Given

  • slope(m)=2.0000slope (m) = 2.0000
  • x−value(x)=7.0000x-value (x) = 7.0000
  • y−value(y)=38.3000y-value (y) = 38.3000

Find

intercept (b)

Start with the thinking

  • The governing relation printed in this handbook section is Slope–intercept line.
  • Everything except b is given, so isolate b 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=mx+by = m x + b
  2. Step 2 — Rearrange the relation so that b stands alone on the left-hand side.

  3. Step 3

    Listthegivens:slope(m)=2.0000,x−value(x)=7.0000,y−value(y)=38.3000List the givens: slope (m) = 2.0000, x-value (x) = 7.0000, y-value (y) = 38.3000
  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    b=24.3000b = 24.3000
  6. Step 6 — Check: returning b = 24.3000 to

    y=mx+by = m x + b

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

Answer:
b=24.3000b = 24.3000

Why the other options are there

  • 48.6000 — kept a factor of two that cancels in the correct rearrangement.
  • 12.1500 — dropped that same factor in the other direction.
  • 26.7300 — rounded an intermediate value before the final step.

Reference: FE Reference Handbook — Mathematics → Straight Line

Example 6
Straight Line — two-point slope — solve for x2 — Straight Line (6)

A surveyor plots a straight line between two staked points. Given x1 (x1) = 4.5000; y1 (y1) = 7.0000; y2 (y2) = 25.5000; slope (m) = 2.6500, determine the x2 (x2).

Given

  • x1(x1)=4.5000x_{1} (x_{1}) = 4.5000
  • y1(y1)=7.0000y_{1} (y_{1}) = 7.0000
  • y2(y2)=25.5000y_{2} (y_{2}) = 25.5000
  • slope(m)=2.6500slope (m) = 2.6500

Find

x2 (x2)

Start with the thinking

  • The governing relation printed in this handbook section is Straight Line — two-point slope.
  • Everything except x2 is given, so isolate x2 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.
  • The FE Handbook Straight Line relation gives the slope through two points on a line.
(1, -3)(10, 12)xyStraight line through two points

Figure 6 — schematic for Straight Line — two-point slope — solve for x2 — Straight Line (6)

Step-by-step solution

  1. Step 1 — State the governing relation:

    m=y2−y1x2−x1m = \dfrac{y_2 - y_1}{x_2 - x_1}
  2. Step 2 — Rearrange symbolically for x2:

    x2=y2−y1m+x1x_{2} = \dfrac{y_2 - y_1}{m} + x_1
  3. Step 3

    Listthegivens:x1(x1)=4.5000,y1(y1)=7.0000,y2(y2)=25.5000,slope(m)=2.6500List the givens: x_{1} (x_{1}) = 4.5000, y_{1} (y_{1}) = 7.0000, y_{2} (y_{2}) = 25.5000, slope (m) = 2.6500
  4. Step 4 — Substitute the given values:

    x2=y2−y12.6500+x1x_{2} = \dfrac{y_2 - y_1}{2.6500} + x_1
  5. Step 5 — Evaluate:

    x2=11.4811x_{2} = 11.4811
  6. Step 6 — Check: returning x2 = 11.4811 to

    m=y2−y1x2−x1m = \dfrac{y_2 - y_1}{x_2 - x_1}

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

Answer:
x2=11.4811x_{2} = 11.4811

Why the other options are there

  • 22.9623 — kept a factor of two that cancels in the correct rearrangement.
  • 5.7406 — dropped that same factor in the other direction.
  • 12.6292 — rounded an intermediate value before the final step.

Reference: FE Handbook — Straight Line

Example 7
Slope–intercept line — solve for x-value — Straight Line (7)

A mathematics problem uses Slope–intercept line. Given slope (m) = 4.9000; intercept (b) = -4.0000; y-value (y) = 42.8000, determine the x-value (x).

Given

  • slope(m)=4.9000slope (m) = 4.9000
  • intercept(b)=−4.0000intercept (b) = -4.0000
  • y−value(y)=42.8000y-value (y) = 42.8000

Find

x-value (x)

Start with the thinking

  • The governing relation printed in this handbook section is Slope–intercept line.
  • Everything except x is given, so isolate x 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=mx+by = m x + b
  2. Step 2 — Rearrange the relation so that x stands alone on the left-hand side.

  3. Step 3

    Listthegivens:slope(m)=4.9000,intercept(b)=−4.0000,y−value(y)=42.8000List the givens: slope (m) = 4.9000, intercept (b) = -4.0000, y-value (y) = 42.8000
  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    x=9.5510x = 9.5510
  6. Step 6 — Check: returning x = 9.5510 to

    y=mx+by = m x + b

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

Answer:
x=9.5510x = 9.5510

Why the other options are there

  • 19.1020 — kept a factor of two that cancels in the correct rearrangement.
  • 4.7755 — dropped that same factor in the other direction.
  • 10.5061 — rounded an intermediate value before the final step.

Reference: FE Reference Handbook — Mathematics → Straight Line

Example 8
Straight Line — two-point slope — solve for slope (case 2) — Straight Line (8)

A designer checks the slope of a straight line on a site grading plan. Given x1 (x1) = 1.5000; x2 (x2) = 11.0000; y1 (y1) = -2.5000; y2 (y2) = 13.0000, determine the slope (m).

Given

  • x1(x1)=1.5000x_{1} (x_{1}) = 1.5000
  • x2(x2)=11.0000x_{2} (x_{2}) = 11.0000
  • y1(y1)=−2.5000y_{1} (y_{1}) = -2.5000
  • y2(y2)=13.0000y_{2} (y_{2}) = 13.0000

Find

slope (m)

Start with the thinking

  • The governing relation printed in this handbook section is Straight Line — two-point slope.
  • Everything except m is given, so isolate m 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.
  • The FE Handbook Straight Line relation gives the slope through two points on a line.
(1, -3)(10, 12)xyStraight line through two points

Figure 8 — schematic for Straight Line — two-point slope — solve for slope (case 2) — Straight Line (8)

Step-by-step solution

  1. Step 1 — State the governing relation:

    m=y2−y1x2−x1m = \dfrac{y_2 - y_1}{x_2 - x_1}
  2. Step 2 — Rearrange symbolically for m:

    m=y2−y1x2−x1m = \dfrac{y_2 - y_1}{x_2 - x_1}
  3. Step 3

    Listthegivens:x1(x1)=1.5000,x2(x2)=11.0000,y1(y1)=−2.5000,y2(y2)=13.0000List the givens: x_{1} (x_{1}) = 1.5000, x_{2} (x_{2}) = 11.0000, y_{1} (y_{1}) = -2.5000, y_{2} (y_{2}) = 13.0000
  4. Step 4 — Substitute the given values:

    m=y2−y1x2−x1m = \dfrac{y_2 - y_1}{x_2 - x_1}
  5. Step 5 — Evaluate:

    m=1.6316m = 1.6316
  6. Step 6 — Check: returning m = 1.6316 to

    m=y2−y1x2−x1m = \dfrac{y_2 - y_1}{x_2 - x_1}

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

Answer:
m=1.6316m = 1.6316

Why the other options are there

  • 3.2632 — kept a factor of two that cancels in the correct rearrangement.
  • 0.8158 — dropped that same factor in the other direction.
  • 1.7947 — rounded an intermediate value before the final step.

Reference: FE Handbook — Straight Line

Example 9
Slope–intercept line — solve for y-value (case 2) — Straight Line (9)

A mathematics problem uses Slope–intercept line. Given slope (m) = 1.3000; x-value (x) = 9.5000; intercept (b) = -1.5000, determine the y-value (y).

Given

  • slope(m)=1.3000slope (m) = 1.3000
  • x−value(x)=9.5000x-value (x) = 9.5000
  • intercept(b)=−1.5000intercept (b) = -1.5000

Find

y-value (y)

Start with the thinking

  • The governing relation printed in this handbook section is Slope–intercept line.
  • 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=mx+by = m x + b
  2. Step 2 — Rearrange the relation so that y stands alone on the left-hand side.

  3. Step 3

    Listthegivens:slope(m)=1.3000,x−value(x)=9.5000,intercept(b)=−1.5000List the givens: slope (m) = 1.3000, x-value (x) = 9.5000, intercept (b) = -1.5000
  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    y=10.8500y = 10.8500
  6. Step 6 — Check: returning y = 10.8500 to

    y=mx+by = m x + b

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

Answer:
y=10.8500y = 10.8500

Why the other options are there

  • 21.7000 — kept a factor of two that cancels in the correct rearrangement.
  • 5.4250 — dropped that same factor in the other direction.
  • 11.9350 — rounded an intermediate value before the final step.

Reference: FE Reference Handbook — Mathematics → Straight Line

Example 10
Straight Line — two-point slope — solve for y2 (case 2) — Straight Line (10)

A drafter verifies a straight line segment on a coordinate layout. Given x1 (x1) = 4.0000; x2 (x2) = 10.5000; y1 (y1) = 9.5000; slope (m) = 1.4000, determine the y2 (y2).

Given

  • x1(x1)=4.0000x_{1} (x_{1}) = 4.0000
  • x2(x2)=10.5000x_{2} (x_{2}) = 10.5000
  • y1(y1)=9.5000y_{1} (y_{1}) = 9.5000
  • slope(m)=1.4000slope (m) = 1.4000

Find

y2 (y2)

Start with the thinking

  • The governing relation printed in this handbook section is Straight Line — two-point slope.
  • Everything except y2 is given, so isolate y2 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.
  • The FE Handbook Straight Line relation gives the slope through two points on a line.
(1, -3)(10, 12)xyStraight line through two points

Figure 10 — schematic for Straight Line — two-point slope — solve for y2 (case 2) — Straight Line (10)

Step-by-step solution

  1. Step 1 — State the governing relation:

    m=y2−y1x2−x1m = \dfrac{y_2 - y_1}{x_2 - x_1}
  2. Step 2 — Rearrange symbolically for y2:

    y2=m(x2−x1)+y1y_{2} = m (x_2 - x_1) + y_1
  3. Step 3

    Listthegivens:x1(x1)=4.0000,x2(x2)=10.5000,y1(y1)=9.5000,slope(m)=1.4000List the givens: x_{1} (x_{1}) = 4.0000, x_{2} (x_{2}) = 10.5000, y_{1} (y_{1}) = 9.5000, slope (m) = 1.4000
  4. Step 4 — Substitute the given values:

    y2=1.4000(x2−x1)+y1y_{2} = 1.4000 (x_2 - x_1) + y_1
  5. Step 5 — Evaluate:

    y2=18.6000y_{2} = 18.6000
  6. Step 6 — Check: returning y2 = 18.6000 to

    m=y2−y1x2−x1m = \dfrac{y_2 - y_1}{x_2 - x_1}

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

Answer:
y2=18.6000y_{2} = 18.6000

Why the other options are there

  • 37.2000 — kept a factor of two that cancels in the correct rearrangement.
  • 9.3000 — dropped that same factor in the other direction.
  • 20.4600 — rounded an intermediate value before the final step.

Reference: FE Handbook — Straight Line

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