TeX source:
\mathtt{(x-3)\cdot(x-3)-(y+5)\cdot(y+5)-(x+y)\cdot(x-y)=(x-3)^{2}-(y-5)^{2}-(x-y)(x+y)=x^{2}-6x+9-y^{2}-10y-25-x^{2}+y^{2}=-6x-10y-16}