Question

Which equation, when graphed, has x-intercepts at (−1, 0) and (−5, 0) and a y-intercept at (0, −30)?

f(x) = −6(x + 1)(x + 5)
f(x) = −6(x − 1)(x − 5)
f(x) = −5(x + 1)(x + 5)
f(x) = −5(x − 1)(x − 5)

Answer 1

f(x) = −6(x + 1)(x + 5)

Reason: x-intercepts −1 and −5 give factors (x+1)(x+5). Let f(x)=a(x+1)(x+5). Then f(0)=5a must equal −30, so a=−6.