某厂一台引风机,07年1月份非计划停运2天,其余时间全出力运行。当年该引风机运行系数是()。
A、99.45%
B、0.55%
C、93.55%
D、6.45%
参考答案:A
— How do you find the new book by JK Rowling?
—__________. I guess she is out of her talent.
A.With the help of my mother.
B.By accident.
C.Very boring
D.In the library.
已知函数f(x)=x3+3ax2+bx+a2在x=﹣1和x=3处有极值.
(1)求a,b的值;
(2)求曲线y=f(x)在x=1处的切线方程.