lim(x->1)ln(x)ln(x-1)
=lim(x->1)ln(x-1)/[1/ln(x)]
=lim(x->1)ln(x-1)'/[1/ln(x)]'
=-lim(x->1)x*lnx*lnx/(x-1)
=-lim(x->1)[lnx*lnx]'/(x-1)'
=-lim(x->1)2*lnx/x=-2*ln1=0