lim(x→0)[(1/x^2)-(1/xtanx)]如题,正确答案是1/3,通过通分之后用洛必达,无穷小代换可以做出来但是我想问的是,在无穷小代换中要注意不是所有的部分都能直接代换,是分子或分母的因式才能,加减

lim(x→0)e^x-x-1/x^2 lim(1-x)^(2/x) x->0 lim(x→0)(1-2x)^1/x 极限? lim 2（1+x）^1/x x→0 极限lim(x→0)(1-2/x)^x lim(x→0) (e^(-1/x^2))/x^100 lim(x→0)(2-e^x)^(1/x) lim(x→0)2x^3-x+1 lim(x→0)(a^2x-1)/4x 求lim(x→0)x cos 1/x lim(x→∞)x^2/ (3x-1)的极限 求lim(1-cosx)/x^2求lim(1-COSX)/X^2X→0 lim(x→0)(1-cos2x)/(x*sin2x) lim(x→0)(xcot2x) lim(x→无穷)(1+(1/2x))^x 1.lim x→0 3x/(sinx-x)2.lim x→0 (1-cosmx)/x^23.lim x→0 sin4x/[(√x+2)-√2]4.lim h →0 [sin(x+h)-sin(x-h)]/h 当x→0时,lim[ln(1+2x)+xf(x)]/x^2=2,求lim[2+f(x)]/x为什么这样解是错的?lim[ln(1+2x)]/x^2+limf(x)/x=lim2x/x^2+limf(x)/x=lim[2+f(x)]/x=2不是有lim[f(x)+g(x)]=limf(x)+limg(x)吗? 当x→0时,lim[ln(1+2x)+xf(x)]/x^2=2,求lim[2+f(x)]/x 为什么这样解是错的?lim[ln(1+2x)]/x^2+limf(x)/x=lim2x/x^2+limf(x)/x=lim[2+f(x)]/x=2不是有lim[f(x)+g(x)]=limf(x)+limg(x)吗? lim x→1 x-1/x^2-x Lim [x^2/(x^2-1)]^x (x→∞) lim(1+x/x)2x (x→∞)