If $f(x) = \begin{cases} \frac{\sqrt{1+kx}-\sqrt{1-kx}}{x} & ; -1 \leq x < 0 \\ \frac{2x+1}{x-1} & ; 0 \leq x \leq 1 \end{cases}$ is continuous at $x=0$,then the value of $k$ is:

Let $f :[0,1] \rightarrow \mathbb{R}$ and $g :[0,1] \rightarrow \mathbb{R}$ be defined as follows:
$f(x) = \begin{cases} 1 & \text{if } x \text{ is rational} \\ 0 & \text{if } x \text{ is irrational} \end{cases}$
$g(x) = \begin{cases} 0 & \text{if } x \text{ is rational} \\ 1 & \text{if } x \text{ is irrational} \end{cases}$
Then:

Discuss the continuity of the function $f$ given by $f(x) = |x|$ at $x = 0$.

Consider the function $f(x) = \begin{cases} \frac{P(x)}{\sin(x-2)}, & x \neq 2 \\ 7, & x = 2 \end{cases}$ where $P(x)$ is a polynomial such that $P''(x)$ is always a constant and $P(3) = 9$. If $f(x)$ is continuous at $x = 2$,then $P(5)$ is equal to:

If $f: R \rightarrow R$ defined by $f(x) = \begin{cases} a^2 \cos ^2 x+b^2 \sin ^2 x, & x \leq 0 \\ e^{ax+b}, & x>0 \end{cases}$ is a continuous function,then:

If $f(x) = \frac{x}{2} - 1$,then on the interval $[0, \pi]$,where $[.]$ represents the greatest integer function,which of the following is true?