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lim=(x²-y²-2x+2y)/(x+ y-2) ① (x,y)→(2,0) ②(x,y)→(0,2) 这个极限多少
人气:239 ℃ 时间:2020-01-30 19:03:01
解答
(x²-y²-2x+2y)/(x+ y-2) =((x+y)(x-y)-2(x-y))/(x+ y-2)
=(x-y)((x+y)-2)/(x+ y-2)
=x-y
① (x,y)→(2,0) =2
②(x,y)→(0,2) =-2
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