I realized that we were missing the middle term
Usually the equation is in the form \(ax^2+bx+c\)
In this case the equation was in this form \(ax^2+c\) it was missing the bx
So that means its difference of squares meaning that middle term canceled out
So anyways it is in the form \(a^2-b^2=(a-b)(a+b)\)
\(81x^2-100=(9x-10)(9x+10)\)
In this case our a=9x and b=10
So \(a^2=(9x)^2=81x^2 \text{ and } b^2=(10)^2=100\)