Verified Answer :

f(x) = x2 (x + 9i)(x - 9i)

Answer:

\(f(x)= x^2(x+9i)(x-9i)\)

Step-by-step explanation:

\(f(x) = x^4 + 81x^2\)

Lets factor GCF x^2

\(f(x) =x^2(x^2+81)\)

Now factor out \(x^2+81\)

LEts find out factors by solving, set the parenthesis =0 and solve for x

\(x^2+81=0\)

Subtract 81 on both sides

\(x^2=-81\)

take square root on both sides

\(x^2=\sqrt{-81}\)

\(\sqrt{-1} =i\)

\(x=i\sqrt{81}\)

\(x=+-9i\)

Two roots are \(x=-9i , x=+9i\)

Factors are \((x+9i)(x-9i)\)

So \(f(x)= x^2(x+9i)(x-9i)\)