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    • Thread Starter

    Okay so I know how to do these (sorta, I was off in the lesson and I've caught up but I'm still not entirely sure!) A question they did in the lesson was:

    1) The sequence u1 u2 u3 is defined by the recurrence relation
    un+1=(-1)^n Un+d
    where d is constant u1=2

    a)Show that U5=2
    b)Deduce an expression for u10 in terms of d
    c) Given that U3=3U2, find the value of d

    I have a lesson tomorrow so I could really do with getting this answered as soon as possible!
    •  Official Rep

     Official Rep
    Sorry you've not had any responses about this. Are you sure you've posted in the right place? Here's a link to our subject forum which should help get you more responses if you post there.

    Just quoting in Fox Corner so she can move the thread if needed :wizard:
    (Original post by Fox Corner)

    For part a you have to go through the sequence. U2=(-1)^2U1+d=d+2
    U3= (-1)^3[d+2]+d=-2 etc etc and U5 turns out to be 2 because of the way that all the ds cancel.

    By looking at the pattern of ds and 2 in the terms you have found you can deduce what U10 is.

    for part c you have U3 and U2 from part a and so can set up the equ and solve for d
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