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    The sequence u1,u2,u3 is defined by the recurrence relation
    Un+1 = (un)^2 -1 N>1
    A) find expressions for u2 and u3 in terms of k
    Given also that u2 + u3=11
    B) find the possible values of k
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    (Original post by Katiekat2000)
    The sequence u1,u2,u3 is defined by the recurrence relation
    Un+1 = (un)^2 -1 N>1
    A) find expressions for u2 and u3 in terms of k
    Given also that u2 + u3=11
    B) find the possible values of k
    are you given an initial value for U1 in terms of k? or do they want you to let U1 = k?
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    I'm assuming you've been given u_1 in terms of k ?

    If so then you just have to use the recurrence relation

    u_2 = u_{1+1} = (u_1)^2 - 1

    etc.

    And for part b use that information to form an equation.
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    (Original post by DylanJ42)
    are you given an initial value for U1 in terms of k? or do they want you to let U1 = k?
    U1 = k
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    (Original post by Katiekat2000)
    U1 = k
    okay so if  U_{n+1} = (U_n)^2 - 1 then

     \displaystyle U_{2} = (U_1)^2 - 1

    and  \displaystyle U_{3} = (U_2)^2 - 1

    can you try sub in  \displaystyle U_1 = k into the first of those two and see what you get for  \displaystyle U_2
 
 
 

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