来自郭卫的问题
如果(x-y)2+M=(x+y)2,那么M等于()A.2xyB.-2xyC.4xyD.-4xy
如果(x-y)2+M=(x+y)2,那么M等于()
A.2xy
B.-2xy
C.4xy
D.-4xy
1回答
2020-07-17 12:50
如果(x-y)2+M=(x+y)2,那么M等于()A.2xyB.-2xyC.4xyD.-4xy
如果(x-y)2+M=(x+y)2,那么M等于()
A.2xy
B.-2xy
C.4xy
D.-4xy
(x-y)2+M=(x+y)2,
x2-2xy+y2+M=x2+2xy+y2,
∴M=4xy.
故答案选:C.