Question

write a polynomial with the zeroes: 5, -3, and -1+2x. I just need help with getting rid of the i. please help me.

Answer 1

(x-5)(x+3)(x-(-1+2i))(x-(-1-2i))= (complex conjugate)

x² - x( -1+2i) - x(-1-2i) + (-1+2i)(-1-2i)
x² - x(-1+2i -1-2i) + (1+2i -2i +4) ---> because i² = -1
x² - x(-2) + (5) = x² + 2x +5

(x-5)(x+3)(x² + 2x +5)=
(x² -2x-15)(x² + 2x +5)=
x^4 -14x² -40x-75