gwd math 16-34

detectiveyang

这一题我给算错了，请问那位给在下解析一下。谢了。

Q34:

If 2x² – y² = 2xy, then (x + y)² =

 

 

A.     x²

B.     3x²

C.     4xy

D.     2y²

E.      – y²

snowflowers

2x^2-y^2 = 2xy i.e y^2 = 2x^2-2xy

(x+y)^2 = x^2+2xy+y^2 = x^2+2xy+2x^2-2xy = 3x^2

detectiveyang

thanks    a   lot !!!!!!!