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Evaluate fd∫-12f(x) dx, where f(x) = |x + 1| + |x| + |x – 1| - Mathematics

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Question

Evaluate `int_(-1)^2 "f"(x)  "d"x`, where f(x) = |x + 1| + |x| + |x – 1|

Sum
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Solution

We can redefine f as f(x) = `{{:(2 - x",",  "if" - 1 < x ≤ 0),(x + 2",",  "if"  0 < ≤ 1),(3x",",  "if"  1 < x ≤ 2):}`

Therefore, `int_(-1)^2 "f"(x)"d"x = int_(-1)^0 (2 - x)"d"x + int_0^1 (x + 2)"d"x + int_1^2 3x"d"x`   ....(By P2)

= `(2x = x^2/2)_(-1)^0 + (x^2/2 + 2x)_0^1 + ((3x^2)/2)_1^2`

= `0 - (-2 - 1/2) + (1/2 + 2) + 3(4/2 - 1/2)`

= `5/2 + 5/2 + 9/2`

= `19/2`.

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Chapter 7: Integrals - Solved Examples [Page 158]

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NCERT Exemplar Mathematics [English] Class 12
Chapter 7 Integrals
Solved Examples | Q 19 | Page 158

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