已知:a²+a-1=0,求a的三次方+2a²+1999的值
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已知:a²+a-1=0,求a的三次方+2a²+1999的值
已知:a²+a-1=0,求a的三次方+2a²+1999的值
已知:a²+a-1=0,求a的三次方+2a²+1999的值
∵a²+a-1=0
∴a(a²+a-1)=0 即a³+a²-a=0
又a³+2a²+1999
=a³+a²-a+a²+a-1+2000
=0+0+2000
=2000
a³+2a²+1999
=a(a²+a)+a²+1999
=a+a²+1999
=2000