微积分：零减正无穷大等于负无穷么 33 34 35 36 怎么做

33、lim[x→-3-] (x²+2x-3)/(x²+x-6)
=lim[x→-3-] (x+3)(x-1) / (x+3)(x-2)
=lim[x→-3-] (x-1) / (x-2)
=-4/(-5)
=4/5
34、lim[x→-(1/2)+] (6x²+x-1)/(4x²-4x-3)
=lim[x→-(1/2)+] (2x+1)(3x-1) / (2x-3)(2x+1)
=lim[x→-(1/2)+] (3x-1) / (2x-3)
=(1/2) / (-2)
=-1/4
35、x→0-时,1/x的极限为-∞,因此本题极限为-∞
36、x→0-时,x²极限为0,1/x的极限为-∞,因此本题极限为+∞
35和36两题看不清楚是“0-”还是“0+”,我按0-做的.
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