得多少..
谢谢..
{√[x-ln(x+a)]}‘
=1/2×[x-ln(x+a)]^(-1/2)×(1-1/(x+a)]
=(x+a-1)/{2(X+a)√[x-ln(x+a)]}
[1-1/(x+a)]/2倍根号下x-ln(x+a)