Question:
Show that the function
$f: R \rightarrow R: f(x)=\left\{\begin{array}{l}1, \text { if } x \text { is rational } \\ -1, \text { if } x \text { is irrational }\end{array}\right.$
is many - one into.
Find
(i) $f\left(\frac{1}{2}\right)$
(ii) $f(\sqrt{2})$
(iii) $f(\pi)$
(iv) $f(2+\sqrt{3})$.
Solution:
(i) $\mathrm{f}\left(\frac{1}{2}\right)$
Here, $x=1 / 2$, which is rational
$\therefore f(1 / 2)=1$
(ii) $\mathrm{f}(\sqrt{2})$
Here, $x=\sqrt{2}$, which is irrational
$\therefore f(\sqrt{2})=-1$
(iii) $f(\pi)$
Here, $x=\Pi$, which is irrational
$f(\pi)=-1$
(iv) $\mathrm{f}(2+\sqrt{3})$.
Here, $x=2+\sqrt{3}$, which is irrational
$\therefore f(2+\sqrt{3})=-1$
Ans. (i) 1 (ii) $-1$ (iii) $-1$ (iv) $-1$
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All Study Material
- JEE Main
- Exam Pattern
- Previous Year Papers
- PYQ Chapterwise
- Physics
- Kinematics 1D
- Kinemetics 2D
- Friction
- Work, Power, Energy
- Centre of Mass and Collision
- Rotational Dynamics
- Gravitation
- Calorimetry
- Elasticity
- Thermal Expansion
- Heat Transfer
- Kinetic Theory of Gases
- Thermodynamics
- Simple Harmonic Motion
- Wave on String
- Sound waves
- Fluid Mechanics
- Electrostatics
- Current Electricity
- Capacitor
- Magnetism and Matter
- Electromagnetic Induction
- Atomic Structure
- Dual Nature of Matter
- Nuclear Physics
- Radioactivity
- Semiconductors
- Communication System
- Error in Measurement & instruments
- Alternating Current
- Electromagnetic Waves
- Wave Optics
- X-Rays
- All Subjects
- Physics
- Motion in a Plane
- Law of Motion
- Work, Energy and Power
- Systems of Particles and Rotational Motion
- Gravitation
- Mechanical Properties of Solids
- Mechanical Properties of Fluids
- Thermal Properties of matter
- Thermodynamics
- Kinetic Theory
- Oscillations
- Waves
- Electric Charge and Fields
- Electrostatic Potential and Capacitance
- Current Electricity
- Thermoelectric Effects of Electric Current
- Heating Effects of Electric Current
- Moving Charges and Magnetism
- Magnetism and Matter
- Electromagnetic Induction
- Alternating Current
- Electromagnetic Wave
- Ray Optics and Optical Instruments
- Wave Optics
- Dual Nature of Radiation and Matter
- Atoms
- Nuclei
- Semiconductor Electronics: Materials, Devices and Simple Circuits.
- Chemical Effects of Electric Current,
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