Which are perfect square trinomials? Select two options.

Question

x2 − 9
x2 −100
x2 − 4x + 4
x2 + 10x + 25
x2 + 15x + 36

Answer 1

it is clear that the first two fail, since they are binomials.

You know that (a+b)^2 = a^2 + 2ab + b^2
so first, check that the first and last terms are perfect squares.
the last three all pass that test.

now just check the middle term. 15 is odd, so it cannot be 2ab.
So, C,E are the answers

Answer 2

Which are perfect square trinomials? Select two options.

x2 − 9
x2 −100
x2 − 4x + 4
x2 + 10x + 25
x2 + 15x + 36