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Deepak Bora
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if (4x^2 + xy ) : (3xy – y^2) = 12 : 5 ,find (x+2y) : (2x+7)

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Ration and proportion

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  1. (4x² + xy )/(3xy – y²) = 12/ 5

    cross multiplying

    5(4x²+xy) = 12(3xy-y²)

    20x² + 5xy = 36xy- 12y²

    divide complete equation by xy

    20x/y +5 = 36 – 12y/x

    20x/y + 12y/x = 36-5

    20x/y +12 y/x = 31

    let x/y = a

    ∴ 20a+ 12/a = 31

    ∴ 20a² – 31a + 12 = 0

    20a² -16a-15a+ 12 = 0

    4a(5a-4)-3(5a-4)=0

    (5a-4)(4a-3)= 0

    ∴ a= 4/5 & a= 3/4

    because x/y = a

    ∴ x/y =4/5    &    x/y =3/4

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