Algebra 1 : Parallel Lines

Study concepts, example questions & explanations for Algebra 1

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Example Questions

Example Question #71 : How To Find Out If Lines Are Parallel

Find a line parallel to the line with the equation:

\displaystyle 5x+5y=10

Possible Answers:

\displaystyle y=x+3

\displaystyle y=\frac{1}{5}x-9

\displaystyle y=-x-2

\displaystyle y=5x+6

Correct answer:

\displaystyle y=-x-2

Explanation:

Lines can be written in the slope-intercept format:

\displaystyle y=mx+b

In this format, \displaystyle m equals the line's slope and \displaystyle b represents where the line intercepts the y-axis.

First, put the given line in \displaystyle y=mx+b form.

\displaystyle 5x+5y=10

We need to isolate \displaystyle y on the left side of the equation. Subtract \displaystyle 5x from both sides of the equation.

\displaystyle 5x-5x+5y=10-5x

Simplify.

\displaystyle 5y=10-5x

Divide both sides of the equation by \displaystyle 5.

\displaystyle \frac{5y}{5}=\frac{10}{5}-\frac{5x}{5}

Simplify.

\displaystyle y=2-x

Rearrange terms to match the slope-intercept form.

\displaystyle y=-x+2

In the given equation:

\displaystyle m=-1

Parallel lines share the same slope.

Only one of the choices has a slope of \displaystyle -1.

\displaystyle y=-x-2

Example Question #541 : Equations Of Lines

Which of the following pairs of lines are parallel?

Possible Answers:

\displaystyle y=2x-5

\displaystyle y=-2x+2

\displaystyle y=4x-2

\displaystyle y=3x+9

\displaystyle y=2x-2

\displaystyle y=2x+12

\displaystyle y=\frac{1}{2}x-8

\displaystyle y=2x-1

Correct answer:

\displaystyle y=2x-2

\displaystyle y=2x+12

Explanation:

Lines can be written in the slope-intercept form:

\displaystyle y=mx+b

In this form, \displaystyle m equals the slope and \displaystyle b represents where the line intersects the y-axis.

Parallel lines have the same slope: \displaystyle m.

Only one choice contains tow lines with the same slope.

\displaystyle y=2x-2

\displaystyle y=2x+12

The slope for both lines in this pair is \displaystyle m=2.

Example Question #73 : How To Find Out If Lines Are Parallel

Find a line parallel to the line with the equation:

\displaystyle 7y-6x=1

Possible Answers:

\displaystyle y=-6x+12

\displaystyle y=\frac{6}{7}x+\frac{1}{2}

\displaystyle y=\frac{7}{6}x+\frac{1}{3}

\displaystyle y=-\frac{6}{7}x-7

Correct answer:

\displaystyle y=\frac{6}{7}x+\frac{1}{2}

Explanation:

Lines can be written in the slope-intercept format:

\displaystyle y=mx+b

In this format, \displaystyle m equals the line's slope and \displaystyle b represents where the line intercepts the y-axis.

First, put the given line in \displaystyle y=mx+b form.

\displaystyle 7y-6x=1

We need to isolate \displaystyle y on the left side of the equation. Add \displaystyle 6x to both sides of the equation.

\displaystyle 7y-6x+6x=1+6x

Simplify.

\displaystyle 7y=1+6x

Divide both sides of the equation by \displaystyle 7.

\displaystyle \frac{7y}{7}=\frac{1}{7}+\frac{6x}{7}

Simplify.

\displaystyle y=\frac{1}{7}+\frac{6}{7}x

Rearrange terms to match the slope-intercept form.

\displaystyle y=\frac{6}{7}x+\frac{1}{7}

In the given equation:

\displaystyle m=\frac{6}{7}

Parallel lines share the same slope.

Only one of the choices has a slope of \displaystyle \frac{6}{7}.

\displaystyle y=\frac{6}{7}x+\frac{1}{2}

Example Question #74 : How To Find Out If Lines Are Parallel

Find a line parallel to the line with the equation:

\displaystyle 9x-5y=16

Possible Answers:

\displaystyle y=-\frac{9}{5}x-1

\displaystyle y=\frac{9}{5}x+5

\displaystyle y=\frac{5}{9}x-\frac{12}{13}

\displaystyle y=9x+2

Correct answer:

\displaystyle y=\frac{9}{5}x+5

Explanation:

Lines can be written in the slope-intercept format:

\displaystyle y=mx+b

In this format, \displaystyle m equals the line's slope and \displaystyle b represents where the line intercepts the y-axis.

First, put the given line in \displaystyle y=mx+b form.

\displaystyle 9x-5y=16

We need to isolate \displaystyle y on the left side of the equation. Subtract \displaystyle 9x from both sides of the equation.

\displaystyle 9x-9x-5y=16-9x

Simplify.

\displaystyle -5y=16-9x

Divide both sides of the equation by \displaystyle -5.

\displaystyle \frac{-5y}{-5}=\frac{16}{-5}-\left ( \frac{9x}{-5} \right )

Simplify. Remember that when a positive number is divided by a negative number, the answer is always negative.

.\displaystyle y=-\frac{16}{5}-\left ( -\frac{9}{5}x\right )

Subtracting a negative number is the same as adding a positive number. Rewrite.

\displaystyle y=-\frac{16}{5}+\frac{9}{5}x

Rearrange terms to match the slope-intercept form.

\displaystyle y=\frac{9}{5}x-\frac{16}{5}

In the given equation:

\displaystyle m=\frac{9}{5}

Parallel lines share the same slope.

Only one of the choices has a slope of \displaystyle \frac{9}{5}.

\displaystyle y=\frac{9}{5}x+5

Example Question #122 : Parallel Lines

Find a line parallel to the line with the equation:

\displaystyle 2x-y=1

Possible Answers:

\displaystyle y=\frac{1}{2}x+\pi

\displaystyle y=-2x-\frac{1}{7}

\displaystyle y=-x-\pi

\displaystyle y=2x+\pi

Correct answer:

\displaystyle y=2x+\pi

Explanation:

Lines can be written in the slope-intercept format:

\displaystyle y=mx+b

In this format, \displaystyle m equals the line's slope and \displaystyle b represents where the line intercepts the y-axis.

First, put the given line in \displaystyle y=mx+b form.

\displaystyle 2x-y=1

We need to isolate \displaystyle y on the left side of the equation. Subtract \displaystyle 2x from both sides of the equation.

\displaystyle 2x-2x-y=1-2x

Simplify.

\displaystyle -y=1-2x

Divide both sides of the equation by \displaystyle -1.

\displaystyle \frac{-y}{-1}=\frac{1}{-1}-\frac{2x}{-1}

Simplify. Remember that when a positive number is divided by a negative number, the answer is always negative.

\displaystyle y=-1-\left ( -2x\right )

Subtracting a negative number is the same as adding a positive number. Rewrite.

\displaystyle y=-1+2x

Rearrange terms to match the slope-intercept form.

\displaystyle y=2x-1

n the given equation:

\displaystyle m=2

Parallel lines share the same slope.

Only one of the choices has a slope of \displaystyle 2.

\displaystyle y=2x+\pi

Example Question #71 : How To Find Out If Lines Are Parallel

Find a line parallel to the line with the equation:

\displaystyle 20y-16x=40

Possible Answers:

\displaystyle y=\frac{5}{4}x-8

\displaystyle y=\frac{4}{5}x+\frac{1}{2}

\displaystyle y=16x+6

\displaystyle y=\frac{1}{4}x-5

Correct answer:

\displaystyle y=\frac{4}{5}x+\frac{1}{2}

Explanation:

Lines can be written in the slope-intercept format:

\displaystyle y=mx+b

In this format, \displaystyle m equals the line's slope and \displaystyle b represents where the line intercepts the y-axis.

First, put the given line in \displaystyle y=mx+b form.

\displaystyle 20y-16x=40

We need to isolate \displaystyle y on the left side of the equation. Add \displaystyle 16x to both sides of the equation.

\displaystyle 20y-16x+16x=40+16x

Simplify.

\displaystyle 20y=40+16x

Divide both sides of the equation by \displaystyle 20.

\displaystyle \frac{20y}{20}=\frac{40}{20}+\frac{16x}{20}

Simplify.

\displaystyle y=2+\frac{16}{20}x

Reduce.

\displaystyle y=2+\frac{4}{5}x

Rearrange terms to match the slope-intercept form.

\displaystyle y=\frac{4}{5}x+2

In the given equation:

\displaystyle m=\frac{4}{5}

Parallel lines share the same slope.

Only one of the choices has a slope of \displaystyle \frac{4}{5}.

\displaystyle y=\frac{4}{5}x+\frac{1}{2}

Example Question #77 : How To Find Out If Lines Are Parallel

Find a line parallel to the line with the equation:

\displaystyle 7y-14x=16

Possible Answers:

\displaystyle y=\frac{1}{2}x-\frac{12}{17}

\displaystyle y=-14x+16

\displaystyle y=-2x+4

\displaystyle y=2x-\frac{4}{7}

Correct answer:

\displaystyle y=2x-\frac{4}{7}

Explanation:

Lines can be written in the slope-intercept format:

\displaystyle y=mx+b

In this format, \displaystyle m equals the line's slope and \displaystyle b represents where the line intercepts the y-axis.

First, put the given line in \displaystyle y=mx+b form.

\displaystyle 7y-14x=16

We need to isolate \displaystyle y on the left side of the equation. Add \displaystyle 14x to both sides of the equation.

\displaystyle 7y-14x+14x=16+14x

Simplify.

\displaystyle 7y=16+14x

Divide both sides of the equation by \displaystyle 7.

\displaystyle \frac{7y}{7}=\frac{16}{7}+\frac{14x}{7}

Simplify.

\displaystyle y=\frac{16}{7}+2x

Rearrange terms to match the slope-intercept form.

\displaystyle y=2x+\frac{16}{7}

In the given equation:

\displaystyle m=2

Parallel lines share the same slope.

Only one of the choices has a slope of \displaystyle 2.

\displaystyle y=2x-\frac{4}{7} 

Example Question #78 : How To Find Out If Lines Are Parallel

Find a line parallel to the line with the equation:

\displaystyle 12y-18x=24

Possible Answers:

\displaystyle y=-18x+24

\displaystyle y=\frac{2}{3}x-2

\displaystyle y=-\frac{3}{2}x+10

\displaystyle y=\frac{3}{2}x-8

Correct answer:

\displaystyle y=\frac{3}{2}x-8

Explanation:

Lines can be written in the slope-intercept format:

\displaystyle y=mx+b

In this format, \displaystyle m equals the line's slope and \displaystyle b represents where the line intercepts the y-axis.

First, put the given line in \displaystyle y=mx+b form.

\displaystyle 12y-18x=24

We need to isolate \displaystyle y on the left side of the equation. Add \displaystyle 18x to both sides of the equation.

\displaystyle 12y-18x+18x=24+18x

Simplify.

\displaystyle 12y=24+18x

Divide both sides of the equation by \displaystyle 12.

\displaystyle \frac{12y}{12}=\frac{24}{12}+\frac{18x}{12}

Simplify.

\displaystyle y=2+\frac{18}{12}x

Reduce.

\displaystyle y=2+\frac{3}{2}x

Rearrange terms to match the slope-intercept form.

\displaystyle y=\frac{3}{2}x+2

n the given equation:

\displaystyle m=\frac{3}{2}

Parallel lines share the same slope.

Only one of the choices has a slope of \displaystyle \frac{3}{2}.

\displaystyle y=\frac{3}{2}x-8

Example Question #81 : How To Find Out If Lines Are Parallel

Find a line parallel to the line with the equation:

\displaystyle y=\frac{1}{2}x+5

Possible Answers:

\displaystyle y=\frac{1}{2}x+\frac{17}{2}

\displaystyle y=-\frac{1}{2}x+6

\displaystyle y=3x+9

\displaystyle y=2x-\frac{4}{5}

Correct answer:

\displaystyle y=\frac{1}{2}x+\frac{17}{2}

Explanation:

Lines can be written in the slope-intercept format:

\displaystyle y=mx+b

In this format, \displaystyle m equals the line's slope and \displaystyle b represents where the line intercepts the y-axis.

In the given equation:

\displaystyle m=\frac{1}{2}

Parallel lines share the same slope.

Only one of the choices has a slope of \displaystyle \frac{1}{2}.

\displaystyle y=\frac{1}{2}x+\frac{17}{2}

Example Question #82 : How To Find Out If Lines Are Parallel

Find a line parallel to the line with the equation:

 \displaystyle y=6x+3

Possible Answers:

\displaystyle y=-6x+6

\displaystyle y=6x-14

\displaystyle y=6

\displaystyle y=\frac{1}{6}x-9

Correct answer:

\displaystyle y=6x-14

Explanation:

Lines can be written in the slope-intercept format:

\displaystyle y=mx+b

In this format, \displaystyle m equals the line's slope and \displaystyle b represents where the line intercepts the y-axis.

In the given equation:

\displaystyle m=6

Parallel lines share the same slope.

Only one of the choices has a slope of \displaystyle 6.

\displaystyle y=6x-14

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