lim(x->1-) lnx.ln(1-x)
=lim(x->1-) ln(1-x)/ (1/lnx) ; ∞/∞ 分子分母分别求导
=lim(x->1-) [-1/(1-x)]/ {-1/[x(lnx)^2] }
=lim(x->1-) x(lnx)^2/(1-x)
=lim(x->1-) x[ln( 1-(1-x)) ] ^2 /(1-x)
=lim(x->1-) x(1-x)^2 /(1-x)
=lim(x->1-) x(1-x)
=0