Polynomial Fractorization Help?

Question

factor Completly:

9x^2 - 25x^2

Answer 1

9x^2 - 25x^2
= x^2(9-25)
= -16x^2

Answer 2

The difference of two perfect squares is:

a² - b² = (a + b)(a - b)

But since your two terms are alike, the answer is:

-16x²

If you had written:

9x² - 25y²

then the answer would be:

(3x + 5y)(3x - 5y)