求极限lim(3x^-2x-1)/(3x(三次方)-x^+5)(x→∞)
问题描述：
求极限lim(3x^-2x-1)/(3x(三次方)-x^+5)(x→∞)
答
(3x²-2x-1)/(3x³-x²+5)
上下同时除以x³
=(3/x-2/x²-1/x³)/(3-1/x+5/x³)
当x趋于无穷时,分子趋于0,分母趋于3
=0/3
=0
省略极限符号lim~