计算:1.(x-2y)(x+2y)²-(x+2y)²;2.(a+b+c)(a+b-c)
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计算:1.(x-2y)(x+2y)²-(x+2y)²;2.(a+b+c)(a+b-c)
计算:1.(x-2y)(x+2y)²-(x+2y)²;2.(a+b+c)(a+b-c)
计算:1.(x-2y)(x+2y)²-(x+2y)²;2.(a+b+c)(a+b-c)
(x-2y)(x+2y)²-(x+2y)²
=(x-2y)(x²+4xy+4y²)-(x²+4xy+4y²)
=x^3+2x²y-4xy²-8y^3-x²-4xy-4y²
2.(a+b+c)(a+b-c)
=a²+2ab+b²-c²
(x-2y)(x+2y)²-(x+2y)²;
=(x-2y)(x^2+4xy+4y^2)-(x^2+4xy+4y^2)
=x^3+4xy+4xy^2-x^2y-8xy^2-8y^3-x^2-4xy-4y^2
=x^3-4xy^2-x^2y-8y^3-x^2-4y^2
2.(a+b+c)(a+b-c)
=(a+b)^2-c^2
=a^b+b^2+2ab-c^2