factor f(x)=4x^(3)+19x^(2)-149x+36 into linear factors if f(x)=-9

1 answer

after a few tries I found f(4) = 0
so (x-4) is a factor
by synthetic long division I got
(x-4)(4x^2 + 35x - 9)
= (x-4)(x+9)(4x - 1)

What does the fact that
f(x) = -9 have to do with it.?

Did you mean to say: f(9) = 0 , that would have given me the clue that x+9 is a factor.