# Example 18 - Chapter 1 Class 12 Relation and Functions

Last updated at Nov. 5, 2018 by Teachoo

Last updated at Nov. 5, 2018 by Teachoo

Transcript

Example 18 Show that if f : A → B and g : B → C are one-one, then gof : A → C is also one-one. Checking gof one-one Suppose gof (x1) = gof (x2) g (f (x1)) = g(f (x2)) As g is one-one So, f (x1) = f (x2), As f is one-one x1 = x2 Hence, gof is one-one.

Composite functions and one-one onto

Chapter 1 Class 12 Relation and Functions

Concept wise

- Relations - Definition
- Empty and Universal Relation
- To prove relation reflexive, transitive, symmetric and equivalent
- Finding number of relations
- Function - Definition
- To prove one-one & onto (injective, surjective, bijective)
- Composite functions
- Composite functions and one-one onto
- Finding Inverse
- Inverse of function: Proof questions
- Binary Operations - Definition
- Whether binary commutative/associative or not
- Binary operations: Identity element
- Binary operations: Inverse

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Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.