设(x+2y)²=(x-2y)²+M,则M等于

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设(x+2y)²=(x-2y)²+M,则M等于
设(x+2y)²=(x-2y)²+M,则M等于

设(x+2y)²=(x-2y)²+M,则M等于
M=(x+2y)²-(x-2y)²
=(x+2y+x-2y)(x+2y-x+2y)
=(2x)(4y)
=8xy

x^2+4y^2+4xy=x^2+4y^2-4xy+M
所以 M=8xy