Let A = Q × Q, where Q is the set of all rational numbers, and

Previous Year Papers

Download Solved Question Papers Free for Offline Practice and view Solutions Online.

Test Series

Take Zigya Full and Sectional Test Series. Time it out for real assessment and get your results instantly.

Test Yourself

Practice and master your preparation for a specific topic or chapter. Check you scores at the end of the test.
Advertisement

 Multiple Choice QuestionsShort Answer Type

381.

Let * be a binary operation on the set Q of rational numbers given as a * b = (2a – b)2, a, b ∈ Q. Find 3 * 5 and 5 * 3. Is 3 * 5 = 5 * 3 ?

136 Views

382. Consider f : R+ → [4, ⊂) given by f(x) = x2 + 4. Show that f is invertible with the inverse f–1 of f given by straight f to the power of negative 1 end exponent left parenthesis straight y right parenthesis equals square root of straight y minus 4 end root where R+ is the set of all non-negative real numbers.
150 Views

383.

Let f : R → R be defined as f (x) = 3 x. Choose the correct answer. (A) f is one-one onto   (B) f is many-one onto  (C) f is one-one but not onto (D) f is neither onc-one nor onto.

123 Views

384.

how that the function f : R* → R* defined by

straight f left parenthesis straight x right parenthesis equals 1 over straight x is one-one and onto, where R* is the set of all non-zero real numbers. Is the result true, if the domain R* is replaced by N with co-domain being same as R*?

116 Views

Advertisement
385. Show that the function f : R →R , defined as f (x) = x2 , is neither one-to-one nor onto.
128 Views

386.

Show that the modulus function f : R → R, given by f (x) = | x |, is neither one-one nor onto, where |x| is x, if x is positive or 0 and | x | is —x, if. x negative.

 

128 Views

387. Find f(A), if f(x) = x2–5x –14 and straight A equals space open square brackets table row 3 cell negative 5 end cell row cell negative 4 end cell 2 end table close square brackets
85 Views

 Multiple Choice QuestionsLong Answer Type

388.

Let A= R × R and * be a binary operation on A defined by

(a, b) * (c, d) = (a+c, b+d)

Show that * is commutative and associative. Find the identity element for *

on A. Also find the inverse of every element (a, b) ∈ A.

1283 Views

Advertisement
Advertisement

389.

Let A = Q × Q, where Q is the set of all rational numbers, and * be a binary operation on A defined by (a, b) * (c, d) = (ac, b+ad) for (a, b), (c, d) element of A. Then find
(i) The identify element of * in A.
(ii) Invertible elements of A, and write the inverse of elements (5, 3) and open parentheses 1 half comma space 4 close parentheses.


Let A = Q x Q, where Q is the set of rational numbers.
Given that * is the binary operation on A defined by (a, b) * (c, d) = (ac, b + ad) for 
(a, b), (c, d) ∈ A.
(i)
We need to find the identity element of the operation * in A.
Let (x, y) be the identity element in A.
Thus,
(a, b) * (x, y) = (x, y) * (a, b) = (a, b), for all (a, b) ∈ A
⇒(ax, b + ay) = (a, b)
⇒ ax = a and b + ay =b
⇒ y = 0 and x = 1
Therefore, (1, 0) ∈ A is the identity element in A with respect to the operation *.

(ii) We need to find the invertible elements of A.
Let (p, q) be the inverse of the element (a, b)
Thus,
left parenthesis straight a comma space straight b right parenthesis asterisk times left parenthesis straight p comma space straight q right parenthesis space equals space left parenthesis 1 comma space 0 right parenthesis
rightwards double arrow space left parenthesis ap comma space straight b plus aq right parenthesis space equals left parenthesis 1 comma space 0 right parenthesis
rightwards double arrow space ap space equals space 1 space and space straight b plus aq space equals space 0
rightwards double arrow space straight p space equals 1 over straight a space space and space straight q equals negative straight b over straight a
space space Thus space the space inverse space elements space of space left parenthesis straight a comma space straight b right parenthesis space is space open parentheses 1 over straight a comma space minus straight b over straight a close parentheses
space space Now space let space us space find space the space inverse space of space left parenthesis 5 comma space 3 right parenthesis space and space open parentheses 1 half comma space 4 close parentheses
space Hence comma space inverse space of space left parenthesis 5 comma space 3 right parenthesis space is space open parentheses 1 fifth comma space minus 3 over 5 close parentheses
And space inverse space of space open parentheses 1 half comma space 4 close parentheses space is space open parentheses 2 comma space fraction numerator negative 4 over denominator begin display style 1 half end style end fraction close parentheses space equals space space left parenthesis 2 comma space minus 8 right parenthesis

1348 Views

Advertisement
390. Let space straight f colon straight W rightwards arrow straight W space be space defined space as
straight f left parenthesis straight n right parenthesis space equals space open curly brackets table row cell straight n minus 1 comma space space if space straight n space is space odd end cell row cell straight n plus 1 comma space if space straight n space is space even end cell end table close curly brackets
Show that f is invertible and find the inverse of f. Here, W is the set of all whole numbers. 
579 Views

Advertisement