Chapter 2 — Functions Overview
Subject
Mathematics (ISC)
Chapter
2 — Functions
Textbook
Chand High School
Dates
23–27 Mar 2026
Learning Objectives
1. Recall types of relations and function concepts from Chapter 1 and Class XI.
2. Distinguish one-one (injective), onto (surjective) and bijective functions with examples.
3. Count one-one, onto and bijective functions using formulas (ⁿPₘ, m!, inclusion-exclusion).
4. Prove a given function is one-one / onto / bijective using standard algebraic method.
5. Define and compute composite functions (f∘g, g∘f); verify associativity and non-commutativity.
6. Define invertible functions; establish necessary & sufficient condition — bijection.
7. Find the inverse of a given function and verify using composition; identify self-inverse functions.
8. Solve application problems including domain restriction questions.
9. Attempt competency-based, Assertion–Reason, Case Study and MCQ-style questions.
2. Distinguish one-one (injective), onto (surjective) and bijective functions with examples.
3. Count one-one, onto and bijective functions using formulas (ⁿPₘ, m!, inclusion-exclusion).
4. Prove a given function is one-one / onto / bijective using standard algebraic method.
5. Define and compute composite functions (f∘g, g∘f); verify associativity and non-commutativity.
6. Define invertible functions; establish necessary & sufficient condition — bijection.
7. Find the inverse of a given function and verify using composition; identify self-inverse functions.
8. Solve application problems including domain restriction questions.
9. Attempt competency-based, Assertion–Reason, Case Study and MCQ-style questions.
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How to Use Each Question
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★ MCQ Questions
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⚠Holidays: 28 Mar (Eid) and 1 Apr (Ram Navami) — no classes on these days.
DAY 1 · FRI 27 MAR 2026
Day 1 — One-one · Onto · Bijective
One-one · Onto · Bijective — Key Definitions
One-onef(x₁)=f(x₂) ⟹ x₁=x₂; equivalently x₁≠x₂ ⟹ f(x₁)≠f(x₂)
OntoRange of f = Co-domain; every y∈B has a pre-image in A
Bijectivef is both one-one and onto
Count 1-1ⁿ⁽ᴮ⁾Pn(A) when n(A)≤n(B); 0 otherwise
Count Bijn! when n(A)=n(B)=n; 0 otherwise
Graph TestOne-one ⟺ any horizontal line meets graph at most once
Day 1 — Examples
✎Concept Board — Day 1Click to open · Draw diagrams & explain concepts▶
Ex 1
Prove f : ℝ→ℝ, f(x) = 2x + 6 is one-one. [Graphical — horizontal line test]
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Ex 2
Show f : ℤ→ℤ, f(x) = x² + x is many-one.
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Ex 3(A)
Number of one-one functions: (i) n(A)=3, n(B)=3 (ii) n(A)=3, n(B)=4 (iii) n(A)=4, n(B)=3.
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Ex 5
State whether f : ℕ→ℕ, f(x) = 5x is injective or surjective.
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Ex 6
Check injectivity and surjectivity: (i) f:ℕ→ℕ, f(x)=x² (iii) f:ℝ→ℝ, f(x)=x² (iv) f:ℕ→ℕ, f(x)=x³.
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Ex 7
Show f:ℝ→ℝ, f(x) = 2x/(1+x²) is neither one-one nor onto. Find set A so that f:ℝ→A is onto.
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Ex 10
f:ℝ→ℝ, f(x) = 4x³+7; show f is a bijection.
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Ex 11
State whether f:ℝ→ℝ, f(x) = 1+x² is one-one / onto / bijective.
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Ex 13
Show f:ℕ→ℕ, f(x) = x+1 (x odd), x−1 (x even) is bijective.
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Ex 19
Number of bijective functions from A={a,b,c} to B={x,y,z}; and when n(B)=4.
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Day 1 — Exercise 2(A)
Q 2
★ f:A→B, A={1,2,3,4}, B={1,2,3,4,5,6}, f(x)=x. Identify the type of function.
(a) One-one but not onto
(b) Onto but not one-one
(c) Both one-one and onto
(d) Neither one-one nor onto
Q 6
f:ℝ→ℝ, f(x)=(2x−7)/4; show f is one-one and onto.
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Q 9
A=ℝ−{3}, B=ℝ−{1}, f:A→B, f(x)=(x−2)/(x−3); is f one-one and onto?
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Q 17
★ A has 6 distinct elements; number of distinct functions that are NOT bijective = ?
(a) 6!
(b) 6⁶−6!
(c) 6⁶
(d) 6!−6
Q 18
A={1,3,5,7}, B={1,2,...,8}; find the number of one-to-one functions from A to B.
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Q 19
★ A={x∈ℕ:x≤5}, B={x∈ℤ:x²−5x+6=0}; number of onto functions from A to B = ?
(a) 2⁵−2
(b) 2⁵
(c) 30
(d) 0
Q 20
★ x = no. of one-one functions from A(3 elements) to B(5 elements); y = one-one from A to A×B. Find relation between x and y.
(a) y = 10x
(b) y = x
(c) 2y = x
(d) y = 2x
Day 1 — Homework
HW 1
Ex 2(A) Q1(a)–(b): For 'is greater than' and 'is the square of' — state R / S / T / E / N.HW 2
Ex 2(A) Q4: f:ℝ→ℝ, f(x)=3x+4; show f is bijective and find f⁻¹.HW 3
Revise counting formulas: one-one (ⁿPₘ), onto (inclusion-exclusion) and bijections (n!).📎 Assignments — Day 1 (Optional · Viewable by students)
A1
A2
A3
Day 1 — Video Resources
Day 1 Exit Ticket
1Define one-one and onto in your own words.
2How many bijections from {a,b,c} to {x,y,z}?
3Is f(x)=x² one-one on ℝ? Why?