当x=-5时,y=7
即a*(-5)^5+b*(-5)^5+c*(-5)-5=7
所以a*5^5+b*5^5+5c+5=-7
a*5^5+b*5^5+5c=-12
当x=5时
y=a*5^5+b*5^5+5c-5
=-12-5
=-17