(1-a+1分之1)×a分之a平方+2a+1,其中a=根号下2-1
=(1-1/(a+1))×(a+1)²/a
=a/(a+1)×(a+1)²/a
=a+1
=√2-1+1
=√2;
如果本题有什么不明白可以追问,