1
WB JEE 2026
MCQ (Single Correct Answer)
+2
-0
Change Language

If $f(x)$ is differentiable for all $x \in \mathbb{R}$ and satisfies the relation

$x=\mathop {\lim }\limits_{n \to \infty }\frac{\left[1^2(f(x))^x\right]+\left[2^2(f(x))^x\right]+\ldots+\left[n^2(f(x))^x\right]}{n^3}$ where [.] denotes the greatest integer function, then $f^{\prime}(x)=$

A

$\frac{1}{3 x^2} \log x$

B

$3 x^{\frac{1}{x}}(1-\log 3 x)$

C

$(3 x)^{\frac{1}{x}}\left[\frac{1-\log 3 x}{x^2}\right]$

D

$(3 x)^{\frac{1}{x}}\left[\frac{\log 3 x-1}{x^2}\right]$

2
WB JEE 2026
MCQ (More than One Correct Answer)
+2
-0
Change Language

If a differentiable function satisfies $(x-y) f(x+y)-(x+y) f(x-y)=2\left(x^2 y-y^3\right) \forall x, y \in \mathbb{R}$ and $f(I)=2$, then

A

$\mathrm{f}(\mathrm{x})$ must be a polynomial function

B

$f(3)=13$

C

$f(3)=12$

D

$f(0)=0$

3
WB JEE 2026
MCQ (More than One Correct Answer)
+2
-0
Change Language

Let $f(x)>0$ for all $x \in \mathbb{R}$ and $f(x)$ is bounded. If $\mathop {\lim }\limits_{n \to \infty } \sum_{r-1}^n a^{r-1} \int_{(r-1) a}^{r a} \frac{f(x) d x}{f(x)+f(2 r a-a-x)}=\frac{3}{5}$ where $0< a< 1$, then the value(s) of a is are

A

$\frac{5}{11}$

B

$\frac{7}{11}$

C

$\frac{1}{11}$

D

$\frac{6}{11}$

4
WB JEE 2026
MCQ (More than One Correct Answer)
+2
-0
Change Language

Consider the curve $x=1-3 t^2, y=t-3 t^3$. The tangent to the curve at the point $t$ is inclined at an angle $\phi$ to OX and the tangent at $\mathrm{P}(-2,2)$ meets the curve again at Q . Then

A

the curve is symmetrical about $x$-axis

B

the curve is symmetrical about $y$-axis

C

$3 t=\tan \phi+\sec \phi$

D

tangents at P and Q are at right angle