Answer:
Step-by-step explanation:
(5) x^2 + 16 is a perfect square binomial only if imaginary roots are allowed.
x^2 + 16 = (x + 4i)(x - 4i)
(6) x^4 + 12x^2 + 36 is a perfect square trinomial.
The square root of x^4 is x^2 and the square root of 36 is 6.
Experimenting, we find that x^4 + 12x^2 + 36 = (x² + 6)²
so we can conclude that x^4 + 12x^2 + 36 = (x² + 6)(x² + 6) = (x² + 6)².