mercy land

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the 2nd, 3rd, and 4th term of an arithemetic progression are x-2, 5 and x+2 respectively, calculate the value of x and hence find the 20th term..

  • mercy land -

    since these are consecutive terms, their difference is the same, so

    5-(x-2) = (x+2)-5
    5-x+2 = x+2-5
    7-x = x-3
    2x = 10
    x = 5

    So, the three terms are 3,5,7

    So, Tn = 1+2(n-1)
    T20 = 1+2(19) = 39

  • new life -

    3(19)=39 : 57=39 : 57-39=18

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