已知a²+a-1=0 求a³+2a²+1999
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已知a²+a-1=0 求a³+2a²+1999
已知a²+a-1=0 求a³+2a²+1999
已知a²+a-1=0 求a³+2a²+1999
a^3+2a^2+1999
=a(a^2+a)-a^2+2a^2+1999
=a^2+a+1999
=1+1999
=2000
a²+a-1=0
∴a²+a=1
∴a³+2a²+1999
=a³+a²+a²+1999
=a(a²+a)+a²+1999
=a+a²+1999
=1+1999
=2000
你好,很高兴回答你的问题
∵a²+a-1=0
∴a²+a=1
∴a³+2a²+1999
=a³+a²+a²+1999
=a(a²+a)+a²+1999
=a*1+a²+1999
=a+a²+1999
=1+1999
=2000
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 2011-04-14
a³+a²-a+a²+a-1+2000
=a﹙a²+a-1﹚+﹙a²+a-1﹚+2000
=2000