SSAT Upper Level Math : How to find the equation of a parallel line

Study concepts, example questions & explanations for SSAT Upper Level Math

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Example Questions

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Example Question #183 : Lines

Find the equation of the line that passes through the point  and is parallel to the line with the equation .

Possible Answers:

Correct answer:

Explanation:

Because the two lines are parallel, we know that the slope of the line we need to find must also be  .

Next, plug in the point given by the question to find the y-intercept of the line.

.

We can then write the equation of the line: 

 

Example Question #1 : How To Find The Equation Of A Parallel Line

Which of these formulas could be a formula for a line perpendicular to the line ?

Possible Answers:

Correct answer:

Explanation:

This is a two-step problem. First, the slope of the original line needs to be found. The slope will be represented by "" when the line is in -intercept form .

So the slope of the original line is . A line with perpendicular slope will have a slope that is the inverse reciprocal of the original. So in this case, the slope would be . The second step is finding which line will give you that slope. For the correct answer, we find the following:

So, the slope is , and this line is perpendicular to the original.

Example Question #184 : Lines

Find the equation of a line that goes through the point  and is parallel to the line with the equation .

Possible Answers:

Correct answer:

Explanation:

For lines to be parallel, they must have the same slope. The slope of the line we are looking for then must be .

The point that's given in the equation is also the y-intercept.

Using these two pieces of information, we know that the equation for the line must be 

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