x3+2x2+3=(x3+x2)+(x2+3)=x2(x+1)+x2+3因为x2+x-1=0,所以x2=1-x所以原式=(1-x)(1+x)+x2+3=1-x2+x2+3=4注：x3为x的三次方，x2为x的二次方
