Find all zeros. Real and Imaginary

Question

f(x)= 5x^4 + 16x^2 + 3

Answer 1

x^2 = (-16 ± √196)/10
= (-16 ± 14)/10
x^2 = -1/5 or x^2 = -3
x = ± i/√5 or x = ± √3 i

All four roots are imaginary