[tex]1.\\x^2-9=0\\
Using\ formula:\\
a^2-b^2=(a-b)(a+b)\\
x^2-9=0\\
x^2-3^2=0\\
(x-3)(x+3)=0\\\\
Asnwer:\ \ x^2-9=(x-3)(x+3)\\\\2.\\x^2+13x=-36\\
x^2+13x+36=0\\ Write\ 13x\ as\ 9x+4x\\x^2+9x+4x+36=0\\ x(x+4)+9(x+4)=0\\(x+4)(x+9)=0\\\\Answer:\ \ x^2+13x+36=(x+4)(x+9)[/tex]