If (2x + 5) is a factor of f(x), for which of the following is f(x) zero?

Correct answer: d f(−5/2)

2x + 5 = 0 gives x = −5/2; since it is a factor, f(−5/2) = 0.

Why the other options are wrong

• a f(−5): −5 is the constant term; 2x + 5 = 0 gives x = −5/2, not x = −5.
• b f(−2): −2 uses the coefficient of x; the value comes from dividing the constant by the coefficient.
• c f(−2/5): −2/5 is the fraction upside down: −b/a = −5/2, not −a/b.