# Thread: Using complex roots to find all zeros of a function.

1. ## Using complex roots to find all zeros of a function.

$2x^3+3x^2+50x+75$

Given: Zero = 5i
so logically -5i is a zero.

then I multiply the two roots and get 25.

then divide Polynomial by 25?
If so, how?

2. Originally Posted by Isimbot
$2x^3+3x^2+50x+75$

Given: Zero = 5i
so logically -5i is a zero.

then I multiply the two roots and get 25.

then divide Polynomial by 25?
If so, how?
$(x-5i)(x+5i) = x^2+25$

$\frac{2x^3+3x^2+50x+75}{x^2+25}$

do the long division to find the last linear factor