Question

factor completely

Z^2-18Z+81-25x^2

I have tried this one several times and just can't seem to get it.

please help

Answer 1

this is a variation of the difference of squares

Z^2-18Z+81-25x^2
= (z-9)^2 - (5x)^2
= (z-9+5x)(z-9-5x)