计算:(1)[(X-Y)^2-(X+Y)(X-Y)]/(-2Y) (2)(2a+1)^2-(2a+1)(2a-1) (3)(2x-y-3)(2x-y+3)
题目
计算:(1)[(X-Y)^2-(X+Y)(X-Y)]/(-2Y) (2)(2a+1)^2-(2a+1)(2a-1) (3)(2x-y-3)(2x-y+3)
答案
(1)[(X-Y)^2-(X+Y)(X-Y)]/(-2Y) =[(x^2-2xy+y^2)-(x^2-y^2)]/(-2y)=[x^2-2xy+y^2-x^2+y^2]/(-2y)=(2y^2-2xy)/(-2y)=x-y(2)(2a+1)^2-(2a+1)(2a-1) =(4a^2+4a+1)-4a^2+1=4a+2(3)(2x-y-3)(2x-y+3)=[(2x-y)-3][(2x-y)+3]...
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