Question 112703
Let w=x+y


So now let's factor {{{w^2 + 6w + 9}}}



*[invoke change_this_name4450 1, 6, 9, "w"]



Now replace w with x+y


{{{(x+y+3)(x+y+3)}}}



So {{{(x+y)^2 + 6(x+y) + 9}}} factors to {{{(x+y+3)(x+y+3)}}}