一、选择题

题目1:已知函数\(f(x)=ax^2+bx+c\),其中\(a\neq 0\),若\(f(1)=2\),\(f(2)=5\),\(f(3)=10\),则\(a+b+c=\)

解析:

由题意得: $\( \begin{cases} a+b+c=2 \\ 4a+2b+c=5 \\ 9a+3b+c=10 \end{cases} \)$

将第一个方程乘以2,得到: $\( \begin{cases} 2a+2b+2c=4 \\ 4a+2b+c=5 \\ 9a+3b+c=10 \end{cases} \)$

将第一个方程从第二个方程中减去,得到: $\( \begin{cases} 2a+2b+2c=4 \\ 2a+b=1 \\ 9a+3b+c=10 \end{cases} \)$

将第一个方程从第三个方程中减去,得到: $\( \begin{cases} 2a+2b+2c=4 \\ 2a+b=1 \\ 6a+2b=6 \end{cases} \)$

将第二个方程乘以2,得到: $\( \begin{cases} 2a+2b+2c=4 \\ 4a+2b=2 \\ 6a+2b=6 \end{cases} \)$

将第二个方程从第三个方程中减去,得到: $\( \begin{cases} 2a+2b+2c=4 \\ 4a+2b=2 \\ 2a=4 \end{cases} \)$

解得:\(a=2\),\(b=-3\),\(c=1\)。

因此,\(a+b+c=2-3+1=0\)。

答案:0

题目2:设\(a>0\),\(b>0\),\(c>0\),若\(a+b+c=3\),则\(\sqrt{a}+\sqrt{b}+\sqrt{c}\)的最大值为

解析:

由柯西不等式得: $\( (a+b+c)(\sqrt{a}+\sqrt{b}+\sqrt{c})^2 \geq (a+b+c)^2 \)$

即: $\( 3(\sqrt{a}+\sqrt{b}+\sqrt{c})^2 \geq 9 \)$

解得: $\( \sqrt{a}+\sqrt{b}+\sqrt{c} \leq 3 \)$

当且仅当\(a=b=c=1\)时,等号成立。

答案:3

二、填空题

题目1:已知函数\(f(x)=x^3-3x^2+4x-1\),则$f’(1)=______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________