Which polynomial is a perfect square trinomial?

25x2 − 20x − 16

9a2 − 30a − 25

25b2 − 15b + 9

16x2 − 24x + 9

Question

Which polynomial is a perfect square trinomial?

 25x2 − 20x − 16

 9a2 − 30a − 25

 25b2 − 15b + 9

 16x2 − 24x + 9

parthkohli · Answer

Do you know what 'discriminant' means?

anonymous · Answer

No not really

anonymous · Answer

A perfect square trinomial is looking for compatible factors that would fit in the last term when multiplied and in the second term if added/subtracted (considering the signs of each polynomials).

parthkohli · Answer

Okay. The discriminant is $b^2 - 4ac$ in a polynomial $ax^2  + bx + c$.

parthkohli · Answer

What you have to do is to find out the discriminants of all these polynomials and pick the one with discriminant = 0.