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Question
If 7x – 15y = 4x + y, find the value of x : y. Hence, use componendo and dividend to find the values of:
`(3x^2 + 2y^2)/(3x^2 - 2y^2)`
Solution
7x – 15y = 4x + y
7x – 4x = y + 15y
3x = 16y
`x/y = 16/3`
`=> x^2/y^2 = 256/9`
`=> (3x^2)/(2y^2) = (768)/18 = 128/3` ...`("Multiplying both sides by" 3/2)`
`=> (3x^2 + 2y^2)/(3x^2 - 2y^2) = (128 + 3)/(128 - 3)` ...(Applying componendo and dividendo)
`=> (3x^2 + 2y^2)/(3x^2 - 2y^2) = 131/125`
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