Question

Use the difference of two squares formula to factor. Be sure to factor out any common factors.

81x^2 - 1

Answer 1

(9x)^2 -1 -> [(3^2)x]^2 -1... don't know if this is what you want, but you might want to just do the quadratic for this., (x+1/9)

Answer 2

81x^2-1
= (9x-1)(9x+1)