已知X+Y=2.求(x方-y方)的平方-8乘(x方+y方)的值

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已知X+Y=2.求(x方-y方)的平方-8乘(x方+y方)的值已知X+Y=2.求(x方-y方)的平方-8乘(x方+y方)的值已知X+Y=2.求(x方-y方)的平方-8乘(x方+y方)的值这类问题出现的

已知X+Y=2.求(x方-y方)的平方-8乘(x方+y方)的值
已知X+Y=2.求(x方-y方)的平方-8乘(x方+y方)的值

已知X+Y=2.求(x方-y方)的平方-8乘(x方+y方)的值
这类问题出现的太多了.
就是一个思路嘛,把式子变换成(x+y)的次方就可以了.
(x²-y²)²-8(x²+y²)
=(x+y)²(x-y)²-8(x²+y²)
=4(x+y)²-16xy-8x²-8y²
=16-8(x+y)²
=16-32
=-16

(x²-y²)²-8*(x²+y²)=(x+y)²(x-y)²-8*(x²+y²)=4(x-y)²-8*(x²+y²)=4x²-8xy+4y²-8x²-8y²
=-4x²-8xy-4y²=-4(x+y)²= -4*4= -16

(x²-y²)²-8*(x²+y²)=(x+y)^2*(x-y)^2-8(x^2+y^2)=4(x-y)^2-8(x^2+y^2)
=4x^2-8xy+4y^2-8x^2-8y^2=-4(x^2+2xy+y^2)=-4(x+y)^2=-4*4=-16

(x²-y²)²-8(x²+y²)
=(x+y)²(x-y)²-8(x²+y²)
=4(x+y)²-16xy-8x²-8y²
=16-8(x+y)²
=16-32
=-16