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    I'm so unsure on how to answer these types of quadratic formula. Please help! -

    "Find a formula for the nth term of this quadratic sequence: 3,5,9,15"

    Please show the method! Thankyou
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    (Original post by jessicaharker51)
    I'm so unsure on how to answer these types of quadratic formula. Please help! -

    "Find a formula for the nth term of this quadratic sequence: 3,5,9,15"

    Please show the method! Thankyou
    If you're given that it's a quadratic sequence then you know that  x_n = an^2 + bn + c where xn is the nth term. (Eg x1 = 3, given when you put n = 1 into the formula on the right) and you need to find a, b and c.

    so think about that, plus the information you're given, and see if you can work out what the sequence is

    I guess you can cut down work by considering the difference between each term, and how that leaves you with less simultaneous equations to work with.
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    (Original post by jessicaharker51)
    I'm so unsure on how to answer these types of quadratic formula. Please help! -

    "Find a formula for the nth term of this quadratic sequence: 3,5,9,15"

    Please show the method! Thankyou
    x_n=an^2+bn+c

    x_1=3=a(1^2)+b(1)+c
    x_2=5=a(2^2)+b(2)+c
    x_3=9=a(3^2)+b(3)+c

    Can you see what you can do from there to find a, b and c??
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    There is an easier way to do it than methods above but it's very difficult and awkward to write how to do it.
 
 
 
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