SAT Math formula sheet · all 24 · Algebra · #2 of 24

Parallel and perpendicular lines on the SAT: How It Is Tested

Linear equations in two variables

Parallel and Perpendicular diagram for the SAT: You can only read the slope in slope-intercept form, so isolate y first. Perpendicular is opposite reciprocal: flip the
What it is really testingYou can only read the slope in slope-intercept form, so isolate y first. Perpendicular is opposite reciprocal: flip the sign AND flip the fraction.

The question from the sheet

Hard
SAT Algebraanswer 1/7
What is the slope of a line that is perpendicular to the line defined by the equation 2y+14x=92y + 14x = 9 in the xyxy-plane?
Student-produced response: 1/7

How the diagram applies

  1. Get the line into y=mx+by = mx + b: 2y=−14x+92y = -14x + 9, so y=−7x+92y = -7x + \tfrac{9}{2}. The slope is −7-7.
  2. Perpendicular means opposite reciprocal: flip −7-7 to −17-\tfrac{1}{7} and change the sign.
  3. The slope is 17\tfrac{1}{7}.

Answer: 1/7

That is 1 of 24.

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Common Questions

It comes up as an SAT linear equations in two variables question. You can only read the slope in slope-intercept form, so isolate y first. Perpendicular is opposite reciprocal: flip the sign AND flip the fraction.

Get the line into y = mx + b: 2y = -14x + 9, so y = -7x + 92. The slope is -7. Perpendicular means opposite reciprocal: flip -7 to -17 and change the sign. The slope is 17.

No. The SAT reference sheet is twelve geometry formulas and three notes, and Parallel and Perpendicular is not one of them. It is one of the 24 things the test expects you to know without being given them. See what the reference sheet does cover at /blog/sat-math-reference-sheet.