SOLUTION: Use the given root to find the solution set of the polynomial equation. x^4 - 21x^2 - 100 = 0 Root = 2i

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Use the given root to find the solution set of the polynomial equation. x^4 - 21x^2 - 100 = 0 Root = 2i      Log On


   

Question 135567: Use the given root to find the solution set of the polynomial equation.
x^4 - 21x^2 - 100 = 0
Root = 2i
Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
x^4 - 21x^2 - 100 = 0
This is a quadratic equation.
Since one root is 2i one of the others is -2i
(x-2i)(x+2i)=x^2+4
(x^4-21x^2-100)/(x^2+4)
=x^2-25 Long division.
=(x-5)(x+5) Factoring.
x=5, x=-5
5, -5 The other two roots.