MCQ
Let $f$ be a real valued continuous function on $[0,1]$ and $f(x)=x+\int\limits_{0}^{1}(x-t) f(t) d t$. Then which of the following points $( x , y )$ lies on the curve $y =f( x )$ ?
  • A
    $(2,4)$
  • B
    $(1,2)$
  • C
    $(4,17)$
  • $(6,8)$

Answer

Correct option: D.
$(6,8)$
d
$f(x)=\left(1+\int\limits_{0}^{1} f(t) d t\right) x-\int\limits_{0}^{1} t f(t) d t$

$f(x)=A x-B$      $\dots(i)$

$A=1+\int\limits_{0}^{1} f(t) d t=1+\int\limits_{0}^{1}(A t-B) d t$

$\Rightarrow A=2(1-B)$      $\dots(ii)$

Also $B=\int\limits_{0}^{1} t f(t) d t=\int\limits_{0}^{1}\left(A t^{2}-B t\right) d t$

 $A=\frac{9}{2} B$      $\dots(iii)$

From $(2),(3)$

 $A=\frac{18}{13}, B=\frac{4}{13}$

so $f(6) =8$

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