If the function f: R R be given by be given by find fog and gof and hence find fog (2) and gof ( −3).
Discuss the commutativity and associativity of binary operation '*' defined on A = Q − {1} by the rule a * b = a − b + ab for all, a, b ∊ A. Also find the identity element of * in A and hence find the invertible elements of A.
Consider f : R+ → [−5, ∞), given by f(x) = 9x2 + 6x − 5. Show that f is invertible with f−1(y).
Hence Find
(i) f−1(10)
(ii) y if f−1(y)=43,
where R+ is the set of all non-negative real numbers.
If a*b denotes the larger of 'a' and 'b' and if a o b = (a*b) + 3, then write the value of (5) o (10), where and o are binary operations.
Let A = { x ∈ Z: 0 ≤ x≤ 12} show that R = {(a,b):a,b ∈ A, |a-b|} is divisible by 4} is an equivalence relation. Find the set of all elements related to 1. Also, write the equivalence class [2].
We have,
R = {(a,b):|a-b|is a multiple of 4}, where a,b ∈ A = {x ∈ Z: 0 ≤ x ≤ 12} = { 0, 1, 2, .....12}
we observe the following properties of relation R.
Reflexivity: For any a ∈ A, we have
|a-a| = 0, which is a multiple of 4.
⇒ (a,a) ∈ R
Thus, (a,a) ∈ R for all a ∈ A
So R, is reflexive.
Symmetry: Let (a,b) ∈ R. Then,
(a,b) ∈ R
⇒ |a-b| is a multiple of 4
⇒|a-b| = 4λ for some λ ∈ N
⇒ |b-a| = 4λ for λ ∈ N
[∵|a-b| = |b-a|]
⇒ (b,a) ∈ R
So, R is symmetric
Transitivity: Let (a,b) ∈ R and (b,c) ∈ R. Then,
(a,b) ∈ R and (b,c) ∈ R
⇒ |a-b| is a multiple of 4 and |b-c| is a multiple of 4
⇒ |a-b| = 4λ and |b-c| = 4μ for some λ, μ ∈ N
⇒ a - b = ±4λ and b-c = ±4μ
⇒ a -c = ±4λ ± 4μ
⇒ a- c is a multiple of 4
⇒ |a-c| is a multiple of 4
⇒ (a,c) ∈ R
Thus, (a,b) ∈ R and (b,c) ∈ R
⇒ (a,c) ∈ R
So, R is transitive
Hence, R is an equivalence relation.
Let x be an element of A such that (x,1) ∈ R Then,
|x-1| is a multiple of 4
⇒ |x-1| = 0,4,8,12
⇒ x -1 = 0,4,8,12
⇒ x = 1,5,9 [∵ 13∉ A]
Hence, the set of all element of A which are related to 1 is {1,5,9} i.e [1] = [1,5,9] &{2} = [2,6,10]
Show that the function f: R → R defined by si neither one- one nor onto. Also, if g: R → R is defined as g(x) = 2x -1 find fog (x)
(i) Is the binary operation *, defined on set N, given by a * b = for all a,b N, commutative?
(ii) Is the above binary operation * associative?
If the binary operation * on the set of integers Z, is defined by a * b = a + 3b2 , then find the value of 2 * 4.