Write the cubic polynomial function f(x) in expanded form with zeros -6, -3, and 1, and given that f(-1) = -80.

Question

f(x) =  ?

Answer 1

f(x) = a(x+6)(x+3(x-1)

f(-1) = a(5)(2)(-2) = -80

a = -80/-20 = 4

f(x) = 4(x+6)(x²+2x-3)

= 4(x³+8x²+9x-18)

= 4x³+32x²+36x-72