题目不对
应该是ax5次方
y=ax^5+bx³+cx-1
则x=-3
y=-a*3^5-b*3³-3c-1=-5
-(a*3^5+b*3³+3c)=-4
a*3^5+b*3³+3c=4
所以x=3
y=a*3^5+b*3³+3c-1
=4-1
=3