x^3+2x^2+x/x^2+2x-8除以（x/x-2 × x+1/x+4)
=x(x^2+2x+1)/(x-2)(x+4) /( x(x+1)/(x-2)(x+4))
=x(x+1)^2/(x-2)(x+4) * (x-2)(x+4)/ x(x+1)
=x+1
=-5/4+1
=-1/4