Question bank / Linear equations in two variables

Math · AlgebraHard

In the xyxy-plane, the graph of 2x+5y=302x + 5y = 30 is translated up 33 units. What is the xx-coordinate of the xx-intercept of the translated graph?

A

1515

B

16.516.5

C

1818

D

22.522.5

Show answer and explanation

Answer: D

Translating a graph up 33 units replaces yy with y−3y - 3: 2x+5(y−3)=302x + 5(y - 3) = 30, or 2x+5y=452x + 5y = 45. At the xx-intercept, y=0y = 0, so 2x=452x = 45 and x=22.5x = 22.5. As a check, the original line has slope −25-\frac{2}{5} and xx-intercept 1515, and raising it 33 units moves the xx-intercept 3÷25=7.53 \div \frac{2}{5} = 7.5 units to the right.

Choice C moves the xx-intercept 33 units to the right, but because the slope is −25-\frac{2}{5}, a vertical shift of 33 moves the xx-intercept 7.57.5 units.

Why the other choices are wrong

  • A. 15 is the x-intercept of the original graph, before the translation.
  • B. This adds 3 to the constant, giving 2x + 5y = 33. Replacing y with y - 3 adds 5 × 3 = 15 to the constant.
  • C. This moves the x-intercept 3 units right, which is a horizontal shift. Moving this line up 3 units moves its x-intercept 7.5 units right.
Ask Owl about this questionNext question

Got it wrong? On SAT Owl, Owl looks at the answer you chose and explains the exact mistake, then gives you similar questions until it sticks. Get your predicted SAT score free, or take a free full-length practice test.