问题补充:
当x=2时,多项式ax5+bx3+cx-5的值为7,当x=-2时,这个多项式的值为A.-17B.-7C.-12D.12
答案:
A
解析分析:根据题意,可知当x=2时,ax5+bx3+cx=12,那么-(ax5+bx3+cx)=-12,从而可知当x=-2时,ax5+bx3+cx=-12,进而可求当x=-2时ax5+bx3+cx-5的值.
解答:根据题意得ax5+bx3+cx-5=7,∴当x=2时,ax5+bx3+cx=12,∴-(ax5+bx3+cx)=-12,即当x=-2时,ax5+bx3+cx=-12,∴ax5+bx3+cx-5=-12-5=-17,故选A.
点评:本题考查了代数式求值、整体代入,解题的关键是理解x的值互为相反数时,ax5+bx3+cx的值也互为相反数.