1.(x-2)(x+2)-(x+1)(x-3)
题目
1.(x-2)(x+2)-(x+1)(x-3)
2.(ab+1)^2-(ab-1)^2
3.(2x-y)^2-4(x-y)(x+2y)
答案
1.(x-2)(x+2)-(x+1)(x-3) =(x^2-4)-(x^2-2x-3) =2x-12.(ab+1)^2-(ab-1)^2 =(ab+1+ab-1)(ab+1-ab+1) =2ab3.(2x-y)^2-4(x-y)(x+2y) =(4x^2-4xy+y^2)-(4x^2+4xy-8y^2) =9y^2-8xy
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