MCQ
$f(x) = f(2 - x),$ then $\int_{\,0.5}^{\,1.5} {\,xf(x)\,dx} $ equals
  • A
    $\int_{\,0}^{\,1} {\,f(x)\,dx} $
  • $\int_{\,0.5}^{\,1.5} {\,f(x)\,dx} $
  • C
    $2\int_{\,0.5}^{\,1.5} {\,f(x)\,dx} $
  • D
    $0$

Answer

Correct option: B.
$\int_{\,0.5}^{\,1.5} {\,f(x)\,dx} $
b
(b) $I = \int_{0.5}^{1.5} {xf\,(x)\,dx = \int_{0.5}^{1.5} {(2 - x)f(2 - x)\,dx} } $,

$\left[ \because \int_{a}^{b}{f(x)dx=\int_{a}^{b}{f(a+b-x)dx}} \right]$ 

$ = \int_{0.5}^{1.5} {(2 - x)f(x)\,dx} = 2\int_{0.5}^{1.5} {f(x)\,dx - I} $

==>$I = \int_{0.5}^{1.5} {f(x)\,dx} $.

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