The zeros for f(x)=x^4-4x^3-9x^2+36x are

x^4 - 4x^3 - 9x^2 + 36x = 0
 x(x^3 - 4x^2 - 9x + 36) = 0
x(x^2(x - 4) - 9(x - 4) = 0
x(x + 3)(x - 3)(x - 4) = 0

the zeroes are  -3, 0, 3, 4  Answer