Question

Which polynomial is a perfect square trinomial?

A. 49x^2 − 28x + 16

B. 4a^2 − 20a + 25

C. 25b^2 − 20b − 16

D. 16x^2 − 24x − 9

Answer 1

B
check first and last terms for square root
must be positive and to be perfect squares
and the second must be equal to first root multiplied with last root by 2
you have:
\[\sqrt{4a ^{2}} = 2a\]
\[\sqrt{25}=\pm 5\]
then :
2(2a)(-5) = -20a