题目

.若a>0,b>0,且函数f(x)=4x3-ax2-2bx+2在x=1处有极值,则ab的最大值等 于 ( ) A.2         B.3         C.6         D.9 答案：D.f′(x)=12x2-2ax-2b, 因为函数f(x)=4x3-ax2-2bx+2在x=1处有极值, 所以f′(1)=12-2a-2b=0, 即a+b=6,则ab≤=9(当且仅当a=b=3时,等号成立). Bob遇到了一些烦恼，请针对他的问题，给出合理的建议。 Bob' s Problems Your Advice A. I, m not popular. 1. Be ________ and helpful. B. I'm in bad health. 2. ________ and eat healthy food. C. I feel nervous before exams. 3. Why not ________? D. Math is difficult for me. 4. You should ask ________ for help. E. My parents don't allow me to watch TV. 5. ________