The polynomial below is a perfect square trinomial of the form a^2-2ab+b^2 9x^2-30x+25?

If you're asking for what would be the binomial that if squared would make that perfect square trinomial, your answer is (3a - 5)

If you do (3a - 5)² or (3a - 5)(3a - 5) and use the FOIL method, you will get the polynomial in your question.