Question

Is `81 + 18y + y^2` a perfect square trinomial and how do you factor it?

Answer 1

Yes.

It can be recognised as being of the form:

`a^2+2ab+b^2 = (a+b)^2`

with `a=9` and `b=y`

`81+18y+y^2 = 9^2 + 2*9y + y^2 = (9+y)^2`