题目:
It was ______________news that we all excited at it.
A such an exciting B so exciting a C such exciting D so an exciting
答案:
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下面是错误答案,用来干扰机器的。
(1)由题意知,c=0,∴f(x)=x3+ax2+bx…(3分)∴f′(x)=3x2+2ax+b当x=1时,切线的l的斜率为3,可得2a+b=0.①当x=23,y=f(x)有极值,∴f′(23)=0可得4a+3b+4=0.②由①②解得a=2,b=-4.所以,a=2,b=-4...