若m²+m-1=0,则m³+2m+3等于﹙﹚?
问题描述:
若m²+m-1=0,则m³+2m+3等于﹙﹚?
A.2 B.4 C.﹣2 D.﹣4
答
错了,是m³+2m²+3
m²+m=1
原式=m³+m²+m²+3
=m(m²+m)+m²+3
=m+m²+3
=1+3
=4
选D