通分、化简、代入求值.
√b/(√a-√b)-√b/(√a+√b)
=[√ab+b-√ab+b]/(a-b)
=2b/(a-b).
当a=√2,b=√3时,
原式=2√3/(√2-√3)
=2√3(√2-√3)/(-1)
=6-2√6.