Question

先化简,再求值:a减1分之1加1减a分之a的和除以a.其中a=根号2加1

Answer 1

[1/(a-1)+a/(1-a)]/a

=[1/(a-1)-a/(a-1)]/a

=[(1-a)/(a-1)]/a

=-1/a

把a=√2+1代入

-1/(√2+1)

=-1(√2-1)/(√2+1)(√2-1)

=1-√2