Question

Answer for number 3

Answer 1

36x^2-49
this closely matches the binomial formula of (a+b)*(a-b)=a^2-b^2
so we know:
a^2=36x^2
a=6x

b^2=49
b=7

so (a+b)*(a-b)=(6x+7)*(6x-7)=36x^2-49