设m^2 + m - 1=0,则m^3 + 2m^2 + 3的值是( )

m²+m-1=0
所以m²+m=1，m²=1-m
m³+2m²+3
=m(1-m)+2m²+3
=m-m²+2m²+3
=m²+m+3
=1+3
=4

用第一个把M 解出来3
带到后面的式子直接解
你当M 就是X..

由题意得``
∵m²+m-1=0
∴m²+m=1，m²=1-m
∴m³+2m²+3
=m(1-m)+2m²+3
=m-m²+2m²+3
=m²+m+3
=1+3
=4