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Published on: 14/09/2019
Relations and Functions
Download CBSE Class 12th Standard CBSE Maths question papers, sample papers, important questions, and previous year solved papers in PDF format. Get free study materials, NCERT solutions, and exam preparation resources for Class 12th Standard CBSE Maths
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1.
If the binary operation * on the set of integers Z is defined by a*b = 3a + b2 then find the value of
(i) 4*3
(ii) 5*2
2.
Let * be a binary operation on the set R defined by a*b = a + b + ab, a, b \(\in R\) Solve the equation 2*(3*x) = 33
3.
Find whether the following operations are binary operation or not
(i) * On N defined by a * b = ab
(ii) * On Z defined by a*b = ab
4.
\(f(x)=x^{ 2 },x\in R\) Find \(\frac { f(1.1)-f(1) }{ 1.1-1 } \)
5.
What is meant by one-one function?
6.
Consider the relation perpendicular on a set of lines in a plane. Show that this relation is symmetric and neither reflexive and nor transitive.
7.
Define Transitive Relation. Give one example.
8.
Define symmetric Relation. Give one example
9.
Define Reflexive. Give one example.
1.
(i) Given a*b = 3a + b2
\(\Rightarrow 4*3=3(4)+(3)^{ 2 }\)
= 12 + 9
4*3 = 21
(ii) Given a*b = 3a + b2
\(\Rightarrow 5*2=3(5)+2^{ 2 }\)
\(\Rightarrow 5*2=15\)
\(\therefore 5*2=19\)
2.
We have 2*(3*x) = 33
\(\Rightarrow 2*(3+x+3x)=33\)
\(\Rightarrow 2*(3+4x)=33\)
\(\Rightarrow 2+(3+4x)+2(3+4x)=33\)
\(\Rightarrow 2+3+4x+6+8x=33\)
\(\Rightarrow 12x+11=33\)
\(\Rightarrow 12x=22\Rightarrow x=\frac { 11 }{ 6 } \)
3.
for a*b = ab is a unique natural number * is a binary operation on N
(ii) Let a = 0, b = 0 , a*b = 0*0 = 00 \(\in Z^{ ' }\)
* is a binary operation on Z
4.
\(f(x)=x^{ 2 },x\in Ra\)
\(f(1.1)=(1.1)^{ 2 }z\)
\(=1.21\)
\(f(1)=(1)^{ 2 }=1\)
\(\frac { f(1.1)-f(1) }{ 1.1-1 } =\frac { 1.21 }{ 1.1-1 } =\frac { 0.21 }{ 0.1 } \)
\(=2.1\)
5.
A function \(f:A\rightarrow B\) is said to be one-one if
\(a\neq b\)
\(\Rightarrow f(a)\neq f(b)for\quad all\quad a,b,\in A\)
or f(a) = f(b)
a = b for all a,b,A
In other words, is one-one, if no two elements of A have same image, i.e., no two elements of A are mapped to same elements of B.
6.
Let the relation \(\bot \) on the set \(\angle \) be denoted by R
For symmetry : \(l_{ 1 }Rl_{ 2 }\Rightarrow l_{ 1 }\bot l_{ 1 }\Rightarrow l_{ 2 }\bot l_{ 1 }Rl_{ 1 }\)
The relation R is symmetric
For reflective \(l_{ 1 }Rl_{ 2 }\Rightarrow l_{ 1 }\bot l\)
No line can be perpendicular to it self
For transitive : \(l_{ 1 }Rl_{ 2 }\Rightarrow l_{ 1 }\) for \(I\ \in \ \angle \)
It is not true
Relation is not transitive
7.
A relation R on a non-empty set A is called a transitive relation if (a, b), (b, c) \(\in R\) then (a, c) \(\in R\) , i.e., aRb, bRc implies aRc.
Thus a relation R on a non empty set A is said to be transitive if there exist a, b, c \(\in A\) such that (a, b)(b, c) \(\in R\) implies (a, c) . \(\in R\)
Example
Let A = (1, 2, 3, 6)
R = (3, 6) (6, 1) (3, 1)
3 R 6 and 6 R 1 \(\Rightarrow \)(3, 1) \(\in R\)
\(\therefore\) A is transitive.
8.
Symmetric Relation : A relation R on a set A is called symmetric relation if aRb implies bRa, for every a,b \(\in a\) i.,e if (a,b) \(\in R\) \(\Rightarrow \) (b,a) \(\in R\)For every a,b \(\in A\)
Example
A = (1,2,3)
A x A =(1,2) (2,1) (1,1) (2,2) (3,3) (1,3) (2,3) (3,1) (3,2 ) \(\in R\)
since (a,b) \(\in R\) (b,a) \(\in R\) for every a, b \(\in A\)
Relation is said to be symmetric
9.
Reflexive Relation : A relation R on a set A is called reflexive relation if aRa for every \(a\in A\) ; if (a, a) \(\in \) R, for every \(a\in A\)
Example let
A = [1, 2, 3]
A x A =(1, 1) (1, 2)(1, 3) (2, 1) (2, 2) (2, 3) (3, 1)(3, 2) (3, 3) \(\in R\)
Since (a, a) \(\in R\) for every \(a\in A\)
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