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Evaluate the following. ∫3ex+42ex-8dx

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Question

Evaluate the following.

`int (3"e"^"x" + 4)/(2"e"^"x" - 8)`dx

Sum
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Solution

Let I = `int (3"e"^"x" + 4)/(2"e"^"x" - 8)`dx

Put, Numerator = A(Denominator) + B[`d/dx`(Denominator)]

Let 3ex + 4 = A(2ex - 8) + B `"d"/"dx"`(2ex - 8)

= 2 Aex - 8A + B(2ex )

∴ 3ex + 4 = (2A + 2B)ex - 8A

Comparing the coefficients of ex and constant term on both sides, we get

2A + 2B = 3 and - 8A = 4

Solving these equations, we get

A = `- 1/2` and B = 2

∴ I = `int (- 1/2 (2"e"^"x" - 8) + 2(2"e"^"x"))/(2"e"^"x" - 8)`dx

`= - 1/2 int "dx" + 2 int ("2e"^"x")/(2"e"^"x" - 8)` dx

∴ I = `- 1/2"x" + 2log |2"e"^"x" - 8|` + c     ...`[int ("f" '("x"))/("f" ("x")) "dx" = log |f ("x")| + "c"]`

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Chapter 5: Integration - EXERCISE 5.3 [Page 123]

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