Question

Let $$f\left( x \right) = {\left( {x + 1} \right)^2} - 1,x \geqslant - 1$$
Statement -1 : The set $$\left\{ x \right.:f\left( x \right) = {f^{ - 1}}\left( x \right) = \left\{ {0, - 1} \right\}$$
Statement-2 : $$f$$ is a bijection.

A. Statement-1 is true, Statement-2 is true. Statement-2 is not a correct explanation for Statement-1.
B. Statement-1 is true, Statement-2 is false.  
C. Statement-1 is false, Statement-2 is true.
D. Statement-1 is true, Statement-2 is true. Statement-2 is a correct explanation for Statement-1.
Answer :   Statement-1 is true, Statement-2 is false.
Solution :
Given that $$f\left( x \right) = {\left( {x + 1} \right)^2} - 1,x \geqslant - 1$$
Clearly $${D_f} = \left[ { - ,\infty } \right)$$   but co-domain is not given. Therefore $$f\left( x \right)$$  need not be necessarily onto.
But if $$f\left( x \right)$$  is onto then as $$f\left( x \right)$$  is one one also, $$\left( {x + 1} \right)$$   being something $$+ve,$$  $${f^{ - 1}}\left( x \right)$$  will exist where $${\left( {x + 1} \right)^2} - 1 = y$$
$$\eqalign{ & \Rightarrow x + 1 = \sqrt {y + 1} \,\left( {{\text{ + ve}}\,{\text{square root as}}\,x + 1 \geqslant 0} \right) \cr & \Rightarrow x = - 1 + \sqrt {y + 1} \Rightarrow {f^{ - 1}}\left( x \right) = \sqrt {x + 1} - 1 \cr & {\text{Then}}\,f\left( x \right) = {f^{ - 1}}\left( x \right) \Rightarrow {\left( {x + 1} \right)^2} - 1 = \sqrt {x + 1} - 1 \cr & \Rightarrow {\left( {x + 1} \right)^2} = \sqrt {x + 1} \Rightarrow {\left( {x + 1} \right)^4} = \left( {x + 1} \right) \cr & \Rightarrow \left( {x + 1} \right)\left[ {{{\left( {x + 1} \right)}^3} - 1} \right] = 0 \Rightarrow x = - 1,0 \cr} $$
$$\therefore $$ The statement-1 is correct but statement-2 is false.

Releted MCQ Question on
Calculus >> Function

Releted Question 1

Let $$R$$ be the set of real numbers. If $$f:R \to R$$   is a function defined by $$f\left( x \right) = {x^2},$$   then $$f$$ is:

A. Injective but not surjective
B. Surjective but not injective
C. Bijective
D. None of these.
Releted Question 2

The entire graphs of the equation $$y = {x^2} + kx - x + 9$$     is strictly above the $$x$$-axis if and only if

A. $$k < 7$$
B. $$ - 5 < k < 7$$
C. $$k > - 5$$
D. None of these.
Releted Question 3

Let $$f\left( x \right) = \left| {x - 1} \right|.$$    Then

A. $$f\left( {{x^2}} \right) = {\left( {f\left( x \right)} \right)^2}$$
B. $$f\left( {x + y} \right) = f\left( x \right) + f\left( y \right)$$
C. $$f\left( {\left| x \right|} \right) = \left| {f\left( x \right)} \right|$$
D. None of these
Releted Question 4

If $$x$$ satisfies $$\left| {x - 1} \right| + \left| {x - 2} \right| + \left| {x - 3} \right| \geqslant 6,$$       then

A. $$0 \leqslant x \leqslant 4$$
B. $$x \leqslant - 2\,{\text{or}}\,x \geqslant 4$$
C. $$x \leqslant 0\,{\text{or}}\,x \geqslant 4$$
D. None of these

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