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Tamil Nadu Board of Secondary EducationHSC Science Class 11

Integrate the following with respect to x: 25xe–5x - Mathematics

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Question

Integrate the following with respect to x:

25xe–5x 

Sum

Solution

`int 5x"e"^(-5x)  "d"x = int  5x"e"^(- 5x)  "d"x`

`int "u"  "dv" = "uv" - "u""'""v"_2 + "u""'""v"_2 - "u""'""v"_3  +`  .........(1)

u = x

u' = 1

u" = 0

dv = `"e"^(- 5x)  * "d"x`

⇒ v = `int "e"^(- 5x) * d"x`

= `("e"^(- 5x))/(- 5)`

v1 = `int "v"  "d"x`

= `- 1/5 int "e"^(-5x) * "d"x`

= `- 1/5 xx ("e"^(- 5x))/(- 5)`

= `+ 1/5^2  "e"^(-5x)`

v2 = `int "v"_1 "d"x`

= `int 1/5^2  "e"^(- 5x)  "d"x`

= `1/5^2 xx ("e"^-5x)/(- 5)`

= `- 1/5^3 "e"^(- 5x)`

`int 25x  "e"^(- 5x)  "d"x = 25[x xx ("e"^(- 5x))/(5x) - 1 xx 1/5^2 "e"^(- 5x) + 0 xx - 1/5^3  "e"^(-5x)]`

= `25[ - x/5  "e"^(- 5x) - 1/5^2 "e"(- 5x)]`

= `- 5x  "e"^(-5 x) - "e"^(- 5x)`

`int 25x  "e"^(- 5x)  "d"x = - "e"^( 5x) (5x + 1 + "c"`

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Chapter 11: Integral Calculus - Exercise 11.7 [Page 210]

APPEARS IN

Samacheer Kalvi Mathematics - Volume 1 and 2 [English] Class 11 TN Board
Chapter 11 Integral Calculus
Exercise 11.7 | Q 1. (iii) | Page 210
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