Hello, I need help with why the problem below is the answer provided. I am pretty good at grouping and everything else... this one problem eludes me for some reason. I just need an explanation how I get from line two to line three. There are no examples in my book and all the other problems like this did not have so many extra variables. I am just not sure what happened to the 2x3(X+Y).
Thanks in advance
(X+Y)^2 + 6(X+Y) +9=
(X+Y)^2 + 2 x 3(X+Y) +3^2=
(X+Y+3)^2
Thanks in advance
(X+Y)^2 + 6(X+Y) +9=
(X+Y)^2 + 2 x 3(X+Y) +3^2=
(X+Y+3)^2