Let A = {1. 2. 3}. Then show that the number of relations contai

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 Multiple Choice QuestionsShort Answer Type

371.

Check the injectivity and surjectivity of the following functions:
f : N → N given by f(x) : x2 


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372.

Check the injectivity and surjectivity of the following functions.

f : Z → Z given by f(x) = x2

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373.

Show that the Signum Function f : R → R, given by

                    straight f left parenthesis straight x right parenthesis space open curly brackets table row cell 1 comma space if space straight x space 0 end cell row cell 0 comma space if space straight x space 0 end cell row cell negative 1 comma space if space straight x space 0 end cell end table close curly brackets

is neither one-one nor onto

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374.

In each of the following cases, state whether the function is one-one, onto or bijective. Justify your answer.

f : R → R defined by f(x) = 3 – 4x

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375.

In each of the following cases, state whether the function is one-one, onto or bijective. Justify your answer.

f : R → R defined by f(x) = 1 + x2

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376. Let A = {1. 2. 3}. Then show that the number of relations containing (1,2) and (2. 3) which are reflexive and transitive but not symmetric is four.


The smallest relation R1 containing (1, 2) and (2, 3) which is reflexive and transitive but not symmetric is {(1, 1), (2. 2), (3, 3), (1, 2), (2, 3), (1, 3)}. Now, if we add the pair (2. 1) to Rto get R2, then the relation R2 will be reflexive, transitive but not symmetric. Similarly, we can obtain R3 and R4 by adding (3, 2) and (3, 1) respectively, to R1 to get the desired relations. However, we can not add any two pairs out of (2, 1), (3, 2) and (3, 1) to R1 at a time, as by doing so, we will be forced to add the remaining third pair in order to maintain transitivity and in the process, the relation will become symmetric also which is not required. the total number of desired relations is four.

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377. Let X = {1, 2, 3, 4, 5, 6, 7, 8, 9}. Let R1 be a relation in X given by R1 = {(x, y) : x – y is divisible by 3} and R2 be another relation on X given by R2 = {(x, y) : {x, y} ⊂ {1,4, 7 }} or ⊂ {2, 5, 8} or {x, y,}⊂ {3, 6, 9}}. Show that R1 = R2.
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378.

Consider the binary operation A on the set {1, 2, 3, 4, 5} defined by a ∧ b = min. {a, b}. Write the operation table of the operation ∧.

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379. Define a binary operation * on the set {0, 1, 2, 3, 4, 5} as

straight a space asterisk times space straight b space equals space open curly brackets table attributes columnalign left end attributes row cell straight a plus straight b space space space space space space space space space space space space space space space space if space straight a plus straight b less than 6 end cell row cell straight a plus straight b minus 6 space space space space space space space space space space space space if space straight a plus straight b greater or equal than 6 end cell end table close

Show that zero is the identity for this operation and each element a of the set is invertible with 6 – a being the inverse of a.
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380.

Let A = Q x Q. Let be a binary operation on A defined by (a, b) * (c, d) = (ac, ad + b).

Then

(i) Find the identify element of (A, *)
(ii) Find the invertible elements of (A, *)

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