若m²+m-1=0,则m³+2m²+3的值为___.
问题描述：
若m²+m-1=0,则m³+2m²+3的值为___.
答
m²+m-1=0 m²+m=0
m³+2m²+3
=m（m²+2m）+3
=m（m²+m+m）+3
=m（1+m）+3
=m+m²+3
=1+3
4