﹙1＋x﹚﹙x的平方＋x分之x-1减x的三次方--x分之1-x﹚
=(1+x)[(x-1)/(x²+x)-(1-x)/(x³-x)]
=(1+x)[(x-1)/x(x+1)+(x-1)/x(x-1)(x+1)]
=(1+x)[(x-1)/x(x+1)+1/x(x+1)]
=(1+x)(x-1+1)/x(x+1)
=(1+x)*x/x(x+1)
=1