MCQ
The sum of the absolute minimum and the absolute maximum values of the function $f(x)=\left|3 x-x^{2}+2\right|-x$ in the interval $[-1,2]$ is
- ✓$\frac{\sqrt{17}+3}{2}$
- B$\frac{\sqrt{17}+5}{2}$
- C$5$
- D$\frac{9-\sqrt{17}}{2}$
$f^{\prime}(x)$ when $x \in\left(-1, \frac{3-\sqrt{17}}{2}\right)$
$f^{\prime}(x)=2 x-4=0 \Rightarrow x=2$
$f^{\prime}(x)=2(x-2) \quad \Rightarrow f^{\prime}(x)$ is always $\downarrow$
$f(2)=2$
$f(-1)=3$
$f\left(\frac{3-\sqrt{17}}{2}\right)=\frac{\sqrt{17}-3}{2}$
$f^{\prime}(x)$ when $x \in\left(\frac{3-\sqrt{17}}{2}, 2\right)$
$f^{\prime}(x)=-2 x+2$
$f^{\prime}(x)=-2(x-1)$
$f^{\prime}(x)=0$ when $x=1$
$f(1)=3$
absolute minimum value $=\frac{\sqrt{17}-3}{2}$
absolute maximum value $=3$
Sum $=\frac{\sqrt{17}-3}{2}+3=\frac{\sqrt{17}+3}{2}$
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$\sqrt{3}$
$\sqrt{2}$
$1$
$0$