当x=-7时
y=a(-7)^5+b(-7)³+c(-7)-5
=-(a7^5+b7³+7c)-5
=7
得 -(a7^5+b7^3+7c)=12
所以 a7^5+b7^3+7c=-12
所以 x=7时
y=a7^5+b7^3+7c-5
=-12-5
=-17