Let $f(x)$ be differentiable function such that $f\left(\dfrac{x+y}{1-xy}\right)=f(x)+f(y) \forall x$ and $y$. If $\underset { x\rightarrow 0 }{ lt } \dfrac { f\left( x \right) ; }{ x } =\dfrac { 1 }{ 3 }$ then $f(1)$ equals& ;

$\lim _{x \rightarrow 3} \frac{x^{3}-27}{x^{2}-9}$ এর মান কোনটি?

$\displaystyle\lim_{x\rightarrow 0}\left(\dfrac{1}{\sin^2x}-\dfrac{1}{\sin h^2x}\right)=?$

$\displaystyle \lim_{x \rightarrow 0}\dfrac {1}{x\sqrt {x}}\left(a\ arc\ tan \dfrac {\sqrt {x}}{a}-b\ arc\ \tan \dfrac {\sqrt {x}}{b}\right)$ has the value equal to

$\lim _{x \rightarrow 2}\left(\frac{x^{2}-2^{x}}{x^{x}-4}\right)$ এর মান কত হবে?