If the function f: R  R  be given by  be given by  find 

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 Multiple Choice QuestionsShort Answer Type

391.

If straight R equals open curly brackets open parentheses straight x comma space straight y close parentheses colon straight x plus 2 straight y space equals space 8 close curly brackets is a relation on N, write the range of R.

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392.

If the function f: R rightwards arrow R  be given by straight f left parenthesis straight x right parenthesis space equals space straight x squared plus 2 space space and space straight g space colon thin space straight R rightwards arrow space straight R be given by straight g left parenthesis straight x right parenthesis space equals fraction numerator straight x over denominator straight x minus 1 end fraction comma space straight x not equal to 1 comma find fog and gof and hence find fog (2) and gof ( −3).


Given that straight f left parenthesis straight x right parenthesis space equals space straight x squared plus 2 space and space straight g left parenthesis straight x right parenthesis space equals space fraction numerator straight x over denominator straight x minus 1 end fraction
Let us find fog:

space fog space equals space straight f open parentheses straight g left parenthesis straight x right parenthesis close parentheses
rightwards double arrow space space fog space equals space open parentheses straight g left parenthesis straight x right parenthesis close parentheses squared plus 2
rightwards double arrow space fog space equals open parentheses fraction numerator straight x over denominator straight x minus 1 end fraction close parentheses squared plus 2
rightwards double arrow fog space equals fraction numerator straight x squared plus 2 left parenthesis straight x minus 1 right parenthesis squared over denominator left parenthesis straight x minus 1 right parenthesis squared end fraction
rightwards double arrow fog space equals fraction numerator straight x squared plus 2 left parenthesis straight x squared minus 2 straight x plus 1 right parenthesis over denominator straight x squared minus 2 straight x plus 1 end fraction
rightwards double arrow fog space equals fraction numerator 3 straight x squared minus 4 straight x plus 2 over denominator straight x squared minus 2 straight x plus 1 end fraction
Therefore, left parenthesis fog right parenthesis space left parenthesis 2 right parenthesis space equals space fraction numerator 3 cross times 2 squared minus 4 cross times 2 plus 2 over denominator 2 squared minus 2 cross times 2 plus 1 end fraction

rightwards double arrow left parenthesis fog right parenthesis thin space left parenthesis 2 right parenthesis space equals space fraction numerator 12 minus 8 plus 2 over denominator 4 minus 4 plus 1 end fraction space equals 6
Now space let space us space find space gof colon
gof space equals space straight g open parentheses straight f left parenthesis straight x right parenthesis close parentheses
rightwards double arrow space space gof space equals space fraction numerator straight f left parenthesis straight x right parenthesis over denominator straight f left parenthesis straight x right parenthesis minus 1 end fraction
rightwards double arrow gof space equals space fraction numerator straight x squared plus 2 over denominator straight x squared plus 2 minus 1 end fraction
rightwards double arrow space gof space equals fraction numerator straight x squared plus 2 over denominator straight x squared plus 1 end fraction

 Therefore comma space left parenthesis gof right parenthesis thin space left parenthesis negative 3 right parenthesis space equals space fraction numerator left parenthesis negative 3 right parenthesis squared plus 2 over denominator left parenthesis negative 3 right parenthesis squared plus 1 end fraction equals space fraction numerator 9 plus 2 over denominator 9 plus 1 end fraction equals 11 over 10

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 Multiple Choice QuestionsLong Answer Type

393.

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. 

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394.

Consider f : R+ → [−5, ∞), given by f(x) = 9x2 + 6x − 5. Show that f is invertible with f−1(y)open parentheses fraction numerator square root of straight y plus 6 end root minus 1 over denominator 3 end fraction close parentheses.

Hence Find
(i) f−1(10)
(ii) y if f−1(y)=43,

where R+ is the set of all non-negative real numbers.

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 Multiple Choice QuestionsShort Answer Type

395.

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.


 Multiple Choice QuestionsLong Answer Type

396.

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].


397.

Show that the function f: R → R defined byf(x) = xx2 + 1, x R si neither one- one nor onto. Also, if g: R → R is defined as g(x) = 2x -1 find fog (x)


 Multiple Choice QuestionsShort Answer Type

398.

If f(x) = x + 7 and g(x) = x – 7, x  R, find (fog) (7)


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 Multiple Choice QuestionsLong Answer Type

399.

(i) Is the binary operation *, defined on set N, given by  a * b = a + b2  for all a,b N, commutative?


(ii) Is the above binary operation * associative?


 Multiple Choice QuestionsShort Answer Type

400.

If the binary operation * on the set of integers Z, is defined by a * b = a + 3b2 , then find the value of 2 * 4.


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