Algebra 1 : Functions and Lines

Study concepts, example questions & explanations for Algebra 1

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Example Questions

Example Question #2 : Perpendicular Lines

Which of the following lines could be perpendicular to the following:

\(\displaystyle y=\frac{3}{4}x-2\)

Possible Answers:

None of the available answers

\(\displaystyle y=\frac{3}{4}x+2\)

\(\displaystyle y=\frac{4}{6}x-17\)

\(\displaystyle y=0\)

\(\displaystyle y=-1\frac{1}{3}x-128\)

Correct answer:

\(\displaystyle y=-1\frac{1}{3}x-128\)

Explanation:

The only marker for whether lines are perpendicular is whether their slopes are the opposite-reciprocal for the other line's slope. The \(\displaystyle y\)-intercept is not important. Therefore, the line perpendicular to \(\displaystyle y=\frac{3}{4}x-2\) will have a slope of \(\displaystyle m=-\frac{4}{3}\) or \(\displaystyle m=-1\frac{1}{3}\)

Example Question #2 : Equations Of Lines

Find a line perpendicular to the line with the equation:

\(\displaystyle y=-8x+1\)

Possible Answers:

\(\displaystyle y=-\frac{1}{8}x-1\)

\(\displaystyle x=8x+2\)

\(\displaystyle y=\frac{1}{8}x-19\)

\(\displaystyle y=-8x-1\)

Correct answer:

\(\displaystyle y=\frac{1}{8}x-19\)

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:

\(\displaystyle m=-8\)

Perpendicular lines have slopes that are negative reciprocals of each other.

First, we need to find its reciprocal.

\(\displaystyle -8\rightarrow-\frac{1}{8}\)

Second, we need to rewrite it with the opposite sign.

\(\displaystyle -\frac{1}{8}\rightarrow\frac{1}{8}\)

Only one of the choices has a slope of \(\displaystyle \frac{1}{8}\).

\(\displaystyle y=\frac{1}{8}x-19\)

Example Question #2 : Equations Of Lines

Find a line perpendicular to the line with the equation:

\(\displaystyle y=\frac{5}{6}x-1\)

Possible Answers:

\(\displaystyle y=\frac{6}{5}x-78\)

\(\displaystyle y=-\frac{5}{6}x\)

\(\displaystyle y=\frac{5}{6}x-8\)

\(\displaystyle y=-\frac{6}{5}x+9\)

Correct answer:

\(\displaystyle y=-\frac{6}{5}x+9\)

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:

\(\displaystyle m=\frac{5}{6}\)

Perpendicular lines have slopes that are negative reciprocals of each other.

First, we need to find its reciprocal.

\(\displaystyle \frac{5}{6}\rightarrow\frac{6}{5}\)

Second, we need to rewrite it with the opposite sign.

\(\displaystyle \frac{6}{5}\rightarrow-\frac{6}{5}\)

Only one of the choices has a slope of \(\displaystyle -\frac{6}{5}\).

\(\displaystyle y=-\frac{6}{5}x+9\)

Example Question #1 : Perpendicular Lines

Find a line perpendicular to the line with the equation:

\(\displaystyle y=-\frac{1}{15}x-12\)

Possible Answers:

\(\displaystyle y=-\frac{1}{15}x+6\)

\(\displaystyle y=15x+6\)

\(\displaystyle y=-15x+6\)

\(\displaystyle y=\frac{1}{15}x+6\)

Correct answer:

\(\displaystyle y=15x+6\)

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:

\(\displaystyle m=-\frac{1}{15}\)

Perpendicular lines have slopes that are negative reciprocals of each other.

First, we need to find its reciprocal.

\(\displaystyle -\frac{1}{15}\rightarrow-\frac{15}{1}\)

Rewrite.

\(\displaystyle -\frac{15}{1}=-15\)

Second, we need to rewrite it with the opposite sign.

\(\displaystyle -15\rightarrow15\)

Only one of the choices has a slope of \(\displaystyle 15\).

\(\displaystyle y=15x+6\) 

Example Question #2 : Perpendicular Lines

Find a line perpendicular to the line with the equation:

\(\displaystyle y=\frac{1}{2}x+79\)

Possible Answers:

\(\displaystyle y=2x-10\)

\(\displaystyle y=-\frac{1}{2}x-10\)

\(\displaystyle y=-2x-10\)

\(\displaystyle y=\frac{1}{2}x-10\)

Correct answer:

\(\displaystyle y=-2x-10\)

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:

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

Perpendicular lines have slopes that are negative reciprocals of each other.

First, we need to find its reciprocal.

\(\displaystyle \frac{1}{2}\rightarrow\frac{2}{1}\)

Rewrite.

\(\displaystyle \frac{2}{1}=2\)

Second, we need to rewrite it with the opposite sign.

\(\displaystyle 2\rightarrow-2\)

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

\(\displaystyle y=-2x-10\)

Example Question #11 : How To Find Out If Lines Are Perpendicular

Find a line perpendicular to the line with the equation:

\(\displaystyle y=\frac{7}{9}x-1\)

Possible Answers:

\(\displaystyle y=-\frac{7}{9}x-8\)

\(\displaystyle y=\frac{9}{7}x+15\)

\(\displaystyle y=\frac{7}{9}x+6\)

\(\displaystyle y=-\frac{9}{7}x+9\)

Correct answer:

\(\displaystyle y=-\frac{9}{7}x+9\)

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:

\(\displaystyle m=\frac{7}{9}\)

Perpendicular lines have slopes that are negative reciprocals of each other.

First, we need to find its reciprocal.

\(\displaystyle \frac{7}{9}\rightarrow\frac{9}{7}\)

Second, we need to rewrite it with the opposite sign.

\(\displaystyle \frac{9}{7}\rightarrow-\frac{9}{7}\)

Only one of the choices has a slope of \(\displaystyle -\frac{9}{7}\).

 

\(\displaystyle y=-\frac{9}{7}x+9\) 

Example Question #12 : Perpendicular Lines

Find a line perpendicular to the line with the equation:

\(\displaystyle y=\frac{5}{2}x-2\)

Possible Answers:

\(\displaystyle y=-5x-7\)

\(\displaystyle y=-\frac{2}{5}x+9\)

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

\(\displaystyle y=\frac{5}{2}x-8\)

Correct answer:

\(\displaystyle y=-\frac{2}{5}x+9\)

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:

\(\displaystyle m=\frac{5}{2}\)

Perpendicular lines have slopes that are negative reciprocals of each other.

First, we need to find its reciprocal.

\(\displaystyle \frac{5}{2}\rightarrow\frac{2}{5}\)

Second, we need to rewrite it with the opposite sign.

\(\displaystyle \frac{2}{5}\rightarrow-\frac{2}{5}\)

Only one of the choices has a slope of \(\displaystyle -\frac{2}{5}\).

 

\(\displaystyle y=-\frac{2}{5}x+9\)

Example Question #13 : Perpendicular Lines

Find a line perpendicular to the line with the equation:

\(\displaystyle y=-\frac{5}{7}x-61\)

Possible Answers:

\(\displaystyle y=\frac{7}{5}x+159\)

\(\displaystyle y=-\frac{7}{5}x-78\)

\(\displaystyle y=\frac{7}{6}x+78\)

\(\displaystyle y=\frac{5}{7}x+97\)

Correct answer:

\(\displaystyle y=\frac{7}{5}x+159\)

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:

\(\displaystyle m=-\frac{5}{7}\)

Perpendicular lines have slopes that are negative reciprocals of each other.

First, we need to find its reciprocal.

\(\displaystyle -\frac{5}{7}\rightarrow-\frac{7}{5}\)

Second, we need to rewrite it with the opposite sign.

\(\displaystyle -\frac{7}{5}\rightarrow\frac{7}{5}\)

Only one of the choices has a slope of \(\displaystyle \frac{7}{5}\).

 

\(\displaystyle y=\frac{7}{5}x+159\)

Example Question #14 : Perpendicular Lines

Find a line perpendicular to the line with the equation:

\(\displaystyle y=\frac{3}{4}x-23\)

Possible Answers:

\(\displaystyle y=-\frac{3}{4}x+84\)

\(\displaystyle y=\frac{4}{3}x-88\)

\(\displaystyle y=\frac{3}{4}x+56\)

\(\displaystyle y=-\frac{4}{3}x+87\)

Correct answer:

\(\displaystyle y=-\frac{4}{3}x+87\)

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:

\(\displaystyle m=\frac{3}{4}\)

Perpendicular lines have slopes that are negative reciprocals of each other.

First, we need to find its reciprocal.

\(\displaystyle \frac{3}{4}\rightarrow\frac{4}{3}\)

Second, we need to rewrite it with the opposite sign.

\(\displaystyle \frac{4}{3}\rightarrow-\frac{4}{3}\)

Only one of the choices has a slope of \(\displaystyle -\frac{4}{3}\).

 

\(\displaystyle y=-\frac{4}{3}x+87\) 

Example Question #15 : Perpendicular Lines

Find a line perpendicular to the line with the equation:

\(\displaystyle y=2x-10\)

Possible Answers:

\(\displaystyle y=-2x+2\)

\(\displaystyle y=2x+2\)

\(\displaystyle y=-\frac{1}{2}\)

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

Correct answer:

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

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.

In the given equation:

\(\displaystyle m=2\)

Perpendicular lines have slopes that are negative reciprocals of each other.

First, we need to find its reciprocal.

\(\displaystyle 2\rightarrow\frac{1}{2}\)

Second, we need to rewrite it with the opposite sign.

\(\displaystyle \frac{1}{2}\rightarrow-\frac{1}{2}\)

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

 

\(\displaystyle y=-\frac{1}{2}x+2\) 

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