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pls help me out in dis ? dat says The 9th term of an Ap is 52 while d 12th term is 70 find d sum of it's 20th term?

  • math -

    S20 = 20/2 (T1+T20)

    d = (T12-T9)/3
    T1 = T9-8d

    Now just plug and chug.

  • math -

    1220

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