已知；m2+m-1=0 求m3+2m2+1997值

题目

已知；m2+m-1=0 求m3+2m2+1997值
m后面为几次方

答案

m2+m-1=0
=>m^2+m=1
m3+2m2+1997
=(m^3+m^2)+m^2+1997
=m(m^2+m)+m^2+1997
=m+m^2+1997
=1+1997
=1998