# How do you know if #9a^2 - 42a + 49# is a perfect square trinomial and how do you factor it?

##### 1 Answer

Jun 3, 2015

Are the first and last terms square? - **Yes**

Is the middle term equal to plus or minus twice the product of the square roots of the first and last terms? - **Yes**

Yes, it is a perfect square trinomial.