若a=1/(√2−1),b=1/(√2+1),则√ab[√(a/b)−√(b/a)]的值为
A、2 B、−2 C、√2 D、2√2
a=1/(√2−1)=(√2+1),b=1/(√2+1)=(√2−1),
√ab[√(a/b)−√(b/a)]
=√a²−√b²
=a−b
=√2+1−√2+1
=2
选择：A、2