-ax^3-[7-(bx+2ax^3)=-ax^3+(bx+2ax^3)-7= ax^3+bx-7
x=2时,代数式-ax^3-[7-(bx+2ax^3)]的值为2,得ax^3+bx-7=2,得ax^3+bx=9
所以,由x=-2时ax^3+bx=-9
所以这个代数式的值=-9-7=-16