先化简,在求值,(x-1分之1-1)除以x的二次方-1分之x的二次方+2x+1,其中x等于根号下2-1

=[1-(x-1)]/(x-1)÷ (x+1)²/(x+1)(x-1)
=(2-x)/(x-1)×(x-1)/(x+1)
=(2-x)/(x+1)
当x=√2-1时
原式=(2-√2+1)/√2
=3√2/2 -1