(-3x+2y)^2-(3x+2y)^2

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(-3x+2y)^2-(3x+2y)^2(-3x+2y)^2-(3x+2y)^2(-3x+2y)^2-(3x+2y)^2原式=[(-3x+2y)+(3x+2y)][(-3x+2y)-(3x+2y)]=

(-3x+2y)^2-(3x+2y)^2
(-3x+2y)^2-(3x+2y)^2

(-3x+2y)^2-(3x+2y)^2
原式=[(-3x+2y)+(3x+2y)][(-3x+2y)-(3x+2y)]
=(4y)(-6x)
=-24xy

令a=1/8+1/16+1/32+1/64+1/128
2a=1/4+1/8+1/16+1/32+1/64+1/64
相减
a=1/4-1/128=31/128
所以1/8+1/16+1/32+1/64+1/128=31/128