Question

若a=根号2-1分之1，b=根号2+1，则根号ab（根号b分之a-根号a分之b）的值为（）

Answer 1

a=b
根号ab（根号b分之a-根号a分之b）
=a-b
=0

Answer 2

a=1/(√2-1)=(√2+1)/[(√2-1)(√2+1)]=√2+1

b=1/(√2+1)=(√2-1)/[(√2-1)(√2+1)]=√2-1

√(ab)*[√(a/b)-√(b/a)]

=√(ab)*√(a/b)-√(ab)*√(b/a)

=a-b

=√2+1-(√2-1)

=2