-ax的三次方-[7-(bx+2ax的三次方)]的值为5
-ax³-7+bx+2ax³
ax³+bx-7
当x=2时
8a+2b-7=5
8a+2b=12
当x=-2时
-8a-2b-7
=-(8a+2b)-7
=-12-7
=-19