解(1)：原式=(6√14)/(8√18)
=(6÷8)×√(14÷18)
=(3/4)×√(7/9)
=(3/4)×(√7)/3
=(√7)/4
(2)：原式=-(√7)/[3√(14/15)]×(3/2)√(5/2)
=-(1÷3×3/2)×√(7÷14/15×5/2)
=-(1/3×3/2)×√(7×15/14×5/2)
=-(1/2)×√(75/4)
=-(1/2)×(5√3)/2
=-(5√3)/4