因为x->1时分子分母都是0,用洛必塔法则,即对分子分母分别求导
limx->1[1－X^(1/2)]/[1－X^(1/3)]
=limx->1[1/2*x^(-1/2)]/[1/3*x^(-2/3)]
=1/2 / 1/3
=3/2