# Lecture - 3 Chapter 2 Relations and Functions

“Don’t be afraid to give up the good to go for the great.” – John D. Rockefeller

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 NCERT EXERCISE 2.3

Question 1. Which of the following relations are functions? Give reasons. If it is a function, determine its domain and range.
(i). {(2,1), (5,1), (8,1), (11,1), (14,1), (17,1)}
(ii). {(2,1), (4,2), (6,3), (8,4), (10,5), (12,6), (14,7)}
(iii). {(1,3), (1,5), (2,5)}.

Question 3. A function f is defined by f(x)=2x – 5. Write down the values of
(i). f(0)
(ii). f(7)
(iii). f(-3)

Question 4. The function ‘t’ which maps temperature in degree Celsius into temperature in degree Fahrenheit is defined by $$t(C)=\frac{9C}{5}+32$$
(i). t(0)
(ii). t(28)
(iii). t(-10)
(iv). The value of C, when t(C) = 212

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 MISCELLANEOUS EXERCISE

Question 2. If $$f(x)=x^2$$, find $$\frac{f(1.1)-f(1)}{(1.1-1)}$$.

Question 7. Let f, g : R→R be defined, respectively by f(x) = x + 1, g(x) = 2x – 3. Find $$f+g, f-g$$ and $$\frac{f}{g}$$.

Question 8. Let $$f={(1,1), (2,3), (0,–1), (–1,–3)}$$ be a function from Z to Z defined by $$f(x)=ax+b$$, for some integers a, b. Determine a, b.

Question 9. Let R be a relation from N to N defined by R = {(a, b) : a, b N and a = b2}. Are the following true?
(i). (a, a) ∈ R, for all a ∈ N
(ii). (a, b) ∈ R, implies (b, a) ∈ R
(iii). (a, b) ∈ R, (b, c) ∈ R implies (a, c) ∈ R.