Math

The first term of an A.P is -8. The ratio of the 7th term to the 9th term is 5:8. Calculate the common difference of the progression

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  1. Where a=-8
    (a+6d)/(a+8d)=5/8

    (6d-8)/(8d-8)=5/8

    It boils down too

    8(3d-4)=5(4d-4)

    2(3d-4)=5(d-1)

    6d-8=5d-1

    d=-1+8=7

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  2. Correction on the last part
    R.H.S

    5(d-1)=5d-5

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  3. 8 - 5 is 3 ie 3 is the common difference

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  4. a = - 8
    Ratio of the 7th and 9th term is a + 6d : a + 8d = 5:8
    8(a+6d) = 5(a+8d)
    8a+48d=5a+40d
    48d - 40d = 5a + 8a
    8d = -3a
    d = -3a÷8
    d = -3×(-8)÷8 = 3
    Therefore common difference = 3

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  5. Science

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  6. Amazing lesson keep it up

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