Question 73604
the degree three polynomial f(x) with real coefficients and leading ocefficient 1, has -3 and +4i among its roots, express f(x) as a product of linear and quadratic polynomials with real coefficients
:
x = -3
is
(x+3)= 0 is the linear part 
:
x = 4i
is
x = Sqrt(-16)
:
Square both sides:
x^2 = -16
x^2 + 16 = 0 is the quadratic part
:
f(x) = (x+3)(x^2 + 16)