Question

Which polynomial is a perfect square trinomial?

9x^2 − 12x + 4

36b^2 − 24b + 16

16x^2 − 24x − 9

4a^2 − 10a − 25

Answer 1

Perfect square has the form \[(a \pm b)^2=a^2 \pm 2ab +b^2\]
So you can see from the first equation that a² = 9x²
This mean a = 3x
You can also see that 4 = b²
So b = 2

Now see if -12x = -2ab
-2ab = 2*3x*3 = -12x

This mean the first equation IS a perfect square.

9x² − 12x + 4 = (3x - 2)²

So you have your answer already. But you could try this out for the other equations, too, for the sake of practice. :)

Answer 2

Alright & thanks.. :) i thought it was the first one :)