【lim 3√(1+x^2) -1 / x^2+2x^3 x→0lim 3√(1+x^2) -1 / x^2+2x^3 x→0它说分母 x^2+2x^3 x^2 为什么?x^2+2x^3 和x^2 怎么会是等价无穷小呢?他们相除不为1

lim x-无穷 (√3x^2+1)/x+1 1、lim(x->无穷大) e^x arctanx2、lim(x->0)sinx√1+sin(1/x)3、lim(x->无穷大)【（√x^2+x+1）-【(√x^2-x+1)】4、lim(x->无穷大)((x+{x+(x)^0.5]^0.5}^0.5)/(2x+1)^0.55、lim(x->0)(sin3x+x^2sin1/x)/((1+cosx)x)6、lim(n->无穷大)(2^n)(si 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 lim（x-3/x+1）^x lim趋向无穷大 lim((√1+x^2)+x)/((√x^3+x)-x)x→+无穷大 数学极限lim(x→0)((x^3)/(3*x^2-1)) lim(x→+无穷)(√x(x+2)-√(x^2-x+1)) lim(x→1)(tan(x-1))/(x^2-1) lim(x->无穷大){(2^x-3^x)/2}^(1/x) lim(x->0)((2-x)/(3-x))^1/x lim(x-sinx)/x^3 x趋于0 不用洛必达法则～为什么不能这样做?=lim(1/x^2)-lim(sinx/x*1/x^2)=lim(1/x^2)-lim(1*1/x^2)=0 求lim√(3-x)-√(1+x)/(x^2+x-2) (x->1) 求lim√(3-x)-√(1+x)/(x^2+x-2) (x->1) lim √（3-x）-√（1+x）/x平方+x-2x→1 1.lim x->∞ （2x/x^2+1)*cosx 2..lim x->∞{ [(x^2-x)arctanx]/x^3-x-5}3..lim x->0 （e^x-e^-x-2x)/(x-sinx) 4..lim x->0 (sinx-x)/(x^3) 5..lim x->0 (x^2*tanx)/(x-tanx) 6..lim x->0 (1+3/x)^2x 7..lim x->0 (1+2x)^(3/sinx) 8.lim x->∞ (x/1+x)^(x-3) 9..li lim(x趋向无穷)-(x+1)+√(x^2+1) 求lim(√x^2+1)-x x→-∞ lim(2x+3/2x+1)^(x+1) lim(2x-3/2x+1）^x+1 lim x->无限大 (1+1/2x) ^ 3x+lnx