lim (x->1)[(x^2+3x-4)/(x^2-1)]=lim (x->1)[(x-1)(x+4)/(x-1)(x+1)]=lim (x->1)[(x+4)(/x+1)]=5/2
lim (x->正无穷)[1+1/(2x)]^3x=lim (x->正无穷){[1+1/(2x)]^(2x)}^(3/2)=e^(3/2)
(lnx)'=1/x、(x-1)'=1
lim (x->1)[(lnx/(x-1)=]lim (x->1)(1/x)=1