ExamGOAL
Books
23
Subjective

If $f(x)=y=\frac{a x-b}{c x-a}$, then prove that $f(y)=x$.

Explanation

We have, $\quad f(x)=y=\frac{a x-b}{c x-a}$

$\begin{aligned} \therefore \quad f(y) & =\frac{a y-b}{c y-a}=\frac{a\left(\frac{a x-b}{c x-a}\right)-b}{c\left(\frac{a x-b}{c x-a}\right)-a} \\ & =\frac{a(a x-b)-b(c x-a)}{c(a x-b)-a(c x-a)}=\frac{a^2 x-a b-b c x+a b}{a c x-b c-a c x+a^2} \\ & =\frac{a^2 x-b c x}{a^2-b c}=\frac{x\left(a^2-b c\right)}{\left(a^2-b c\right)}=x \\ \therefore \quad f(y) & =x\quad \text{Hence proved.}\end{aligned}$

24
MCQ (Single Correct Answer)

Let $n(A)=m$ and $n(B)=n$. Then, the total number of non-empty relations that can be defined from $A$ to $B$ is

A
$m^n$
B
$n^m-1$
C
$m n-1$
D
$2^{m n}-1$
25
MCQ (Single Correct Answer)

If $[x]^2-5[x]+6=0$, where $[\cdot]$ denote the greatest integer function, then

A
$x \in[3,4]$
B
$x \in(2,3]$
C
$x \in[2,3]$
D
$x \in[2,4)$
26
MCQ (Single Correct Answer)

Range of $f(x)=\frac{1}{1-2 \cos x}$ is

A
$\left[\frac{1}{3}, 1\right]$
B
$\left[-1, \frac{1}{3}\right]$
C
$(-\infty,-1] \cup\left[\frac{1}{3}, \infty\right)$
D
$\left[-\frac{1}{3}, 1\right]$
27
MCQ (Single Correct Answer)

Let $f(x)=\sqrt{1+x^2}$, then

A
$f(x y)=f(x) \cdot f(y)$
B
$f(x y) \geq f(x) \cdot f(y)$
C
$f(x y) \leq f(x) \cdot f(y)$
D
None of these