已知多项式ax5+bx3+cx+7,当x=4时,该多项式的值是72,则当x=-4时,它的值是_.

问题描述:

已知多项式ax5+bx3+cx+7,当x=4时,该多项式的值是72,则当x=-4时,它的值是______.

当x=4时,
ax5+bx3+cx+7
=1024a+64b+4c+7=72,
所以1024a+64b+4c=65,
当x=-4时,
ax5+bx3+cx+7
=-1024a-64b-4c+7
=-(1024a+64b+4c)+7
=-65+7
=-58.
故答案为:-58.