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In the sequence: x+4y ; 2y+2 ;x ;y-1, (consisting of 4 terms) the first three terms form an arithmetric progression, while the last three tern form a geometric sequence. Calculate the values of x and y. Answer(s) can be left in surd form.

  • maths -

    "the first three terms form an arithmetric progression"
    so....
    2y+2 - (x+4y) = x - (2y+2)
    which gives x = 2

    "the last three tern form a geometric sequence"
    so ...
    x/(2y+2) = (y-1)/x , but we know x = 2

    2/(2y+2) = (y-1)/2

    I get y = ±√3

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