The linear function f has slope −2 and f(0) = 5. For what value of x does f(x) = −9?

Question

Accepted Answer

A. 7. f(x) = −2x + 5. Solving −2x + 5 = −9 gives −2x = −14, so x = 7.

Answer

B. −7 — x = −7 gives f(−7) = 14 + 5 = 19, not −9. Watch the sign when dividing by −2.

Answer

C. 2 — x = 2 gives f(2) = 1. Set −2x + 5 equal to −9 and solve.

Answer

D. −2 — x = −2 gives f(−2) = 9, the opposite of the target −9.

Algebra practice question