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Using componendo and dividendo, find the value of x: 3x+4+3x-53x+4-3x-5=9 - Mathematics

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Question

Using componendo and dividendo, find the value of x:

`(sqrt(3x + 4) + sqrt(3x - 5))/(sqrt(3x + 4) - sqrt(3x - 5)) = 9`

Sum

Solution

`(sqrt(3x + 4) + sqrt(3x - 5))/(sqrt(3x + 4) - sqrt(3x - 5)) = 9/1`

Applying componendo and dividend, we have

`(sqrt(3x + 4) + sqrt(3x - 5) + sqrt(3x + 4) - sqrt(3x - 5))/(sqrt(3x + 4) + sqrt(3x - 5) - sqrt(3x + 4) + sqrt(3x - 5)) = (9 + 1)/(9 - 1)`

`=> (2sqrt(3x + 4))/(2sqrt(3x - 5)) = 5/4`

Squaring both sides, we have

`(3x + 4)/(3x - 5) = 25/16`

`=>` 16(3x + 4) = 25(3x – 5)

`=>` 48x – 64 = 75x – 125

`=>` 75x – 48x = 64 + 125

`=>` 27x = 189

`=> x = 189/27`

`=>` x = 7

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Chapter 7: Ratio and Proportion (Including Properties and Uses) - Exercise 7 (D) [Page 102]

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Selina Mathematics [English] Class 10 ICSE
Chapter 7 Ratio and Proportion (Including Properties and Uses)
Exercise 7 (D) | Q 21 | Page 102

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