1)

The total  number of distincts  $x \epsilon  [0,1]$ for which   $\int_{0}^{x} \frac{t^{2}}{1+t^{4}}dt=2x-1$  is


A) 0

B) 1

C) 2

D) 3

Answer:

Option B

Explanation:

Let  $f(x)=\int_{0}^{x} \frac{t^{2}}{1+t^{4}}dt$

   $\Rightarrow f'(x)=\frac{x^{2}}{1+x^{4}}>0$  , for all $x \epsilon  [0,1]$

  $\therefore$    f(x) is increasing
  At   x=0, f(0)=0    and x=1,

  $f(1)=\int_{0}^{1} \frac{t^{2}}{1+t^{4}}dt$

Because,   $0<\frac{t^{2}}{1+t^{4}}<\frac{1}{2}$

$\Rightarrow$      $\int_{0}^{1} 0.dt <\int_{0}^{1} \frac{t^{2}}{1+t^{4}}dt<\int_{0}^{1} \frac{1}{2}.dt$

$\Rightarrow$    $0<f(1)<\frac{1}{2}$

 Thus, f(x) can be plotted as,

 2322021825_m22.PNG

$\therefore$   y= f(x) and  y=2x-1 can be shown as

2322021678_m23.PNG

From the graph , the total number of distinct solutions for  $x \epsilon  [0,1]$ = 1

                               [ as they intersect only at one point]