[x-1-8/(X-1)]÷（x+3）/（x+1）
=[(x-1)^2-8]/(x-1)*(x+1)/(x+3)
=[(x-1)^2-8]*(x+1)/[(x-1)(x+3)]
=[(x-1+2√2)(x-1-2√2]（x+1)/[(x-1)(x+3)]
=[(3-√2-1+2√2)(3-√2-1-2√2](3-√2+1)/[(3-√2-1)(3-√2+3)]
=(2+√2)(2-3√2)(4-√2)/[(2-√2)(6-√2)]
=-14√2/[14-8√2]
=-(56+49√2)/17 .