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Let F (X) =`{ (1 + X, 0≤ X ≤ 2) , (3 -x , 2 < X ≤ 3):}` Find Fof.

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Question

Let

f (x) =`{ (1 + x, 0≤ x ≤ 2) , (3 -x , 2 < x ≤ 3):}`

Find fof.

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Solution

f (x) =`{ (1 + x, 0≤ x ≤ 2) , (3 -x , 2 < x ≤ 3):}`

It can be written as,

f (x) = `{ (1 +x , 0 ≤ x ≤ 1) , (1 +x, 1< x ≤ 2) ,( 3 - x, 2 < x ≤ 3):}`

When, 0 ≤ x ≤ 1

Then , `f (x) = 1 +x `

Now when , 0 ≤ x ≤ 1 then ,1 ≤ x + 1 ≤ 2

Then , `f (f(x))` = 1 + (1 + x ) = 2 + x   [ ∵ 1 ≤ f (x) < 2]

When ,1 < x ≤ 2

Then , f (x) = 1 + x

Now when , 1 < x ≤ 2 then,2 < x +1 ≤ 3

Then , f (f(x)) = 3 − ( 1+ x ) = 2 − x  [ ∵ 2 ≤ f(x) <3 ]

When , 2 < x ≤ 3

Then , f (x) = 3 - x

Now when ,2< x ≤ 3 then ,0 ≤ 3 − x < 1

Then , f (f(x)) = 1 + ( 3 − x ) = 4 − x     [ ∵ 0 ≤ f (x) < 1 ]

f(f(x)) = ` {(2 + x , 0 ≤ x ≤ 1) , (2 -x, 1 < x ≤ 2),( 4- x , 2 < x ≤ 3):}`

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Chapter 2: Functions - Exercise 2.3 [Page 55]

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R.D. Sharma Mathematics Volume 1 and 2 [English] Class 12
Chapter 2 Functions
Exercise 2.3 | Q 12 | Page 55

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