SAT Math Multiple Choice Question 929: Answer and Explanation
13. If (x, y) is a solution to the system of equations above, what is the value of y2?
- A. 12
- B. 16
- C. 120
- D. 144
Correct Answer: D
Category: Passport to Advanced Math / Quadratics
Strategic Advice: When you encounter a system of equations in which one of the equations is already solved for a variable, substitute its value into the other equation and solve.
Getting to the Answer: The second equation tells you that y is equal to 3x, so substitute 3x for y in the first equation. Then solve for x2 (not x because x2 will be more useful when solving for y2):
Now, substitute 16 for x2 in the first equation and solve for y2:
The correct answer is (D).