MCQ
Let $f(x)=\max \{|x+1|,|x+2|, \ldots,|x+5|\}$. Then $\int_{-6}^{0} f(x) d x$ is equal to
  • A
    $20$
  • B
    $40$
  • $21$
  • D
    $41$

Answer

Correct option: C.
$21$
c
$f(x)=\max \{|x+1|,|x+2|,|x+3|,|x+4|,|x+5|\}$

$\int_{-6}^{0} f(x) d x=\int_{-6}^{-3}|x+1| d x+\int_{-3}^{0}|x+5| d x$

$=-\int_{-6}^{-3}(x+1) d x+\int_{-3}^{0}(x+5) d x$

$=-\left[\frac{x^{2}}{2}+x\right]_{-6}^{-3}+\left[\frac{x^{2}}{2}+5 x\right]_{-3}^{0}$

$=-\left[\left(\frac{9}{2}-3\right)-(18-6)\right]+\left[0-\left(\frac{9}{2}-15\right)\right]$

$=-\left[\frac{3}{2}-12\right]+\frac{21}{2}=\frac{21}{2}+\frac{21}{2}=21$

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