若a*a+3a-1=0,则a*a*a+5a*a+5 - 知识问答

若a*a+3a-1=0,则a*a*a+5a*a+5a+18=?可将平方立方写成简写

3个回答

即a²+3a=1
原式=a³+3a²+2a²+5a+18
=a(a²+3a)+2a²+5a+18
=a×1+2a²+5a+18
=2a²+6a+18
=2(a²+3a)+18
=2×1+18
=20

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