Find the complex zeros of the polynomial function Write f in

Find the complex zeros of the polynomial function. Write f in factored form. f(x)=x^4+17x^2+16

f(x)=x^4+17x^2+16

Let x^2 = y .So,

y^2 +17y +16 =0

Solve the quadratice equation by using te formula:

x= (-b +/- sqrt(b^2 -4ac) )/2a

y = ( -17 +/- sqrt(17^2 -4*16) )/2

y = -16 , -1

Now x^2=y : x^2 = -16 ---> x = +/- 4i

x^2 = -1 -----> x = +/- i

Roots : x= -i , i , 4i ,-4i