Question

已知a平方-a-1=0,那么a三次方-2a+3的值

详细点，另外的看不懂
为什么是这样的啊？

Answer 1

a平方-a-1=0
a^2=a+1
a^3=a^2+a
所以a三次方-2a+3=a^2-a+3=a+1-a+3=4

Answer 2

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

Answer 3

a^2=a+1
a^3=a*a^2=a(a+1)=a^2+a=(a+1)+a=2a+1
a^3-2a+3=(2a+1)-2a+3=4

Answer 4

∵a²-a-1=0
∴a²-2=a-1
a³-2a+3=a(a²-2)+3=a(a-1)+3=a²-a+3=4

Answer 5

解：a^2-a-1=0
a^3-2a+3=a(a^2-a-1)+(a^2-a-1)+4=0+0+4=4
本题用配凑法

Answer 6

a平方-a-1=0 可知a平方=a+1
a三次方-2a+3=a(a平方-2)+3=a(a+1-2)+3=a(a-1)+3=a平方-a+3
因为a平方-a-1=0,a平方-a=1
a平方-a+3=1+3=4