Maths (srithematic progression)

If the 4th term of an A.P is twice the 8th term, prove that the 10th term is twice the 11th term.

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  1. 4th term --- a + 3d
    8th term ---- a + 7d

    a+3d = 2(a+7d)
    a+3d = 2a + 14d
    -a = 11d
    a = -11d

    11th term = a + 10d
    = -11d + 10d
    = -d

    10th term = a + 9d
    = -11d + 9d
    = -2d = twice -d = twice 11th term

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