若x+y的三次方-xy(x+y)=(x+y)乘以A,则A为

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若x+y的三次方-xy(x+y)=(x+y)乘以A,则A为
若x+y的三次方-xy(x+y)=(x+y)乘以A,则A为

若x+y的三次方-xy(x+y)=(x+y)乘以A,则A为
(x+y)^3-xy(x+y)=(x+y)A,
∴A=(x+y)^2-xy
=x^2+xy+y^2.

(x+y)³-xy(x+y)=(x+y)A,
左右两边同÷(x+y)原式变形为
(x+y)²-xy=A

(x+y)³-xy(x+y)=A(x+y)
同时除以(x+y)得(x+y)²-xy=A
化简得x²+y²-xy=A