(x+y)^2=11,(x-y)^2=7,求xy的值
问题描述:
(x+y)^2=11,(x-y)^2=7,求xy的值
答
∵(X+Y)=X+2XY+Y=11 (X-Y)=X-2XY+Y=7 ∴(X+Y)-(X-Y)=4XY=11-7=4 ∴XY=1
(x+y)^2=11,(x-y)^2=7,求xy的值
∵(X+Y)=X+2XY+Y=11 (X-Y)=X-2XY+Y=7 ∴(X+Y)-(X-Y)=4XY=11-7=4 ∴XY=1