Which polynomial is a perfect square trinomial?

a. 25^x2 - 20x - 16

b. 9a^2 - 30a - 25

c. 25b^2 - 15b 9

d. 16x^2 - 24x 9?

A polynomial is a perfect square trinomial if in form

a^2x^2-2ab+b^2

look at each

we can eliminate A and B since we have - b^2 not + b^2

look at the rest

C. 5^2b-3*5*b+3^2

nope

D. 4^2x^2-2*4*3x+3^3

yes

answe is D (factors to (4x-9) ^2)