Solution:
Given that, (x+3y)^{2}+2(x+3y)(x-y)+(x-y)^{2}.
Clearly this is in the form of (a+b)^{2}=a^{2}+2ab+(b)^{2}.
Here a = x+3y and b = x-y
Substitute these values in the formula, we get,
= (x+3y+x-y)^{2}.
= (2x+2y)^{2}.

Directions: Solve the following problems. Also write at least 10 examples of your own.