Question

先化简 再求值.(a-1分之3a剪a+1分之a)乘以a分之a²剪1 其中a=2剪根号2

Answer 1

.(a-1分之3a剪a+1分之a)乘以a分之a²剪1

=[3a/(a-1)-a/(a+1)]×(a+1)(a-1)/a

=3a/(a-1)×(a+1)(a-1)/a-a/(a+1)×(a+1)(a-1)/a

=3(a+1)-(a-1)

=2a+4

∵a=2剪根号2

∴原式=4-2√2+4

=8-2√2