Consider the sequence of numbers $(1,2,3, \ldots \ldots, 13)$. A person choose three numbers at random from the sequence. The probability that the chosen three number form an A.P. is
$\frac{21}{157}$
$\frac{18}{143}$
$\frac{29}{180}$
$\frac{24}{163}$
If $f(x)=\frac{1+x}{1-x}$ and $A$ is a matrix such that $A^3=0$, then $f(A)=$
$1+2 \mathrm{~A}+2 \mathrm{~A}^2$
$1+2 A+A^2$
$1-2 \mathrm{~A}+\mathrm{A}^2$
$1+A+A^2$
Which of the following statements is always true?
If $f(x)$ is decreasing, then $\frac{1}{f(x)}$ is increasing
If $f(x)$ is decreasing, then $\frac{1}{f(x)}$ is also decreasing
If both $f$ and $g$ are positive functions such that $f$ is decreasing and $g$ is increasing, then $\frac{f}{g}$ is a decreasing function
If both $f$ and $g$ are positive functions such that $f$ is increasing and $g$ is decreasing then $\frac{f}{g}$ is a decreasing furnction
If $0<\alpha<\beta<\gamma<\frac{\pi}{2}$, then the equation $\frac{1}{x-\sin \alpha}+\frac{1}{x-\sin \beta}+\frac{1}{x-\sin \gamma}=0$ has
real and unequal roots
imaginary roots
real and equal roots
rational roots
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