Question

先化简 再计算 (x+2)(x-1)分之1+x÷(x-2+x+2分之3)其中x=2分之1

Answer 1

(1+x)/[ (x+2)(x-1)]÷[x-2+3/(x+2)]

=(1+x)/[ (x+2)(x-1)]÷[(x²-4+3)/(x+2)]

=(1+x)/[ (x+2)(x-1)]÷[(x²-1)/(x+2)]

=(1+x)/[(x+2)(x-1`)]×(x+2)/[(x+1)(x-1)]

=1/(x-1)²

∵x=1/2

∴原式=1/(1/2-1)²=4