## Discussion

If x + y = k, then 3x2 + 6xy + 3y2 =

 (A) k (B) ... (C) ... (D) ... (E) ... (F) ...
*This question is included in Nova Math - Diagnostic: Test / Review, question #14

The solution is

Posted: 12/29/2011 14:45
I don't understand why (x^2+2xy+y^2) equals (x+y)+2. Thanks
Posted: 12/29/2011 16:07
Charlene, factoring out 3 yields 3 (x^2 + 2xy + y^2). Inside the parentheses is the perfect square of (x+y), so the polynomial inside the parentheses equals (x+y)^2 -- not (x+y)+2 as you mentioned. Then you substitute (x+y) with k, which gives you 3k^2, E.
Posted: 11/30/2012 05:42
How did you remove the 2xy from the equation 3(x^2+2xy+y^2) then made it 3(x+y)^2 ?
Posted: 12/29/2011 19:37
Oh ok thank you :)
Posted: 01/07/2012 17:49
Joel, why would you factor out 3?
Posted: 01/07/2012 17:50
Nevermind I see
Posted: 11/30/2012 05:44
Oh it's the formula, okay I got it
Posted: 12/05/2012 11:28
Here's a brief explanation for those who are confused or can't "get the point".
3x^2 + 6xy + 3y^2 = 3((x+y)^2)=3k^2 (E).
Posted: 12/28/2012 13:10
I don't get how to do this?
Posted: 12/29/2012 11:59
Square both sides first and then multiply both sides by 3 You need to be signed in to perform that action.