已知:a²+a-1=0,求a³+2a²+1999

问题描述:

已知:a²+a-1=0,求a&sup3+2a²+1999

a²+a-1=0
a²+a=1
a³+2a²+1999
=a(a²+a+a)+1999
=a(1+a)+1999
=a²+a+1999
=1+1999
=2000