已知a平方-a-1=0,那么a三次方-2a+3的值

已知a平方-a-1=0,那么a三次方-2a+3的值

a三次方-2a+3
=a³-a²-a+a²-a-1+4
=a(a²-a-1)+(a²-a-1)+4
=0+0+4
=4

a平方-a-1=0 -->a^2-a=1
a^2-1=a
a^3-2a+3
=a^3-a-a+3
=a(a^2-1)-a+3
=a^2-a+3
=1+3=4