Hi, could someone please explain, in stages how to complete a question I have been trying to finish for a while, thanks.
I'm new to this and cannot insert pictures, sorry.
Sum of (from 1 to n) r[3^(r-1)]=¼[3^n(2n-1)+1]
Last edited by helpstoask; 07-05-2012 at 16:18.
An outline of steps to get to the right answer will be:
Step 1: Show that it's true for ;
Step 2: Note that and apply the induction hypothesis to the big bracket;
Step 3: Rearrange stuff.
If you're still stuck, show your working and we'll see where you're going wrong.
[For typing maths into TSR, look at the Guide to LaTeX.]
Last edited by nuodai; 07-05-2012 at 16:30.
Last edited by nuodai; 07-05-2012 at 16:51.
(Original post by helpstoask)
I get to =¼[3^k(2k-1)+1+4(k+1)3^k]
Then I cannot continue
Now try to simplify,
Last edited by raheem94; 07-05-2012 at 16:53.
I suggested expanding it all for a reason, students with less ability than you struggle with anything but the simplest factorisation.
(Original post by nuodai)
Right, so you have
Take out the
as a common factor to get
Can you see what to do now, given what you've been told so far?
Hint: simplify the bracket after
and then look for common factors.
Last edited by Mr M; 07-05-2012 at 16:53.
Reason: Point proved!