当x=2时,多项式ax5+bx3+cx-5的值为7,则当x=-2时,求这个多项式的值.

问题描述:

当x=2时,多项式ax5+bx3+cx-5的值为7,则当x=-2时,求这个多项式的值.

x=2时,ax5+bx3+cx-5=a×25+b×23+2c-5=7,
∴32a+8b+2c=12,
当x=-2时,ax5+bx3+cx-5,
=a×(-2)5+b×(-2)3+(-2)c-5,
=-32a-8b-2c-5,
=-12-5,
=-17.