limx趋向于2 ,5x/x^2-4=?

limx趋向于-2(x-4)/(x+2)=-4 求证明 用极限定义哦~ limx趋向于无穷x^2+2x-4/x^3-x^2 limx趋向于-1(3x^2-5x-2)/（4x^2-2x+1）的极限 limx趋向于0(2x-1)^5/((2x+1)^2(1-3x)^2) 求极限limx趋向于1x^2+2x+5/x^2+1 limx趋向于无穷2x^2-4/3x^2-x limx趋向于无穷时4x^3-2x+8/3x^2+1 计算极限：limx趋向于无穷,[（5x^2+1）/(3x-1)]sin1/x limx趋向于无穷大((2+e^(1/x))/(1+e^(4/x)+sinx/|x|) limx趋向于0,x^2/ln(1-3x)=? limx趋向于无穷大x^2(1-cox1/x)=多少 limx趋向无穷大,(1+1/x)^3x+2=?