Verified answer

1)       [tex]36a^2-49b^2\\6^{2} a^{2} -49b^{2} \\6^{2} a^{2}-7^{2} b^{2} \\(6a)^{2} -7^{2} b^{2} \\(6a)^{2} -(7b)^{2} \\(6a-7b)*(6a+7b)[/tex]

2)[tex]x^2-8xy+16y^2\\x^{2} -2*x*4y+16y^{2} \\x^{2} -2*x*4y+4^{2} y^{2} \\x^{2} -2*x*4y+(4y)\x^{2} \\(x-4y)^{2}[/tex]