Proving the Sum of Reciprocals by Induction

  • Thread starter Thread starter thefeedinghan
  • Start date Start date
  • Tags Tags
    Induction Proof
thefeedinghan
Messages
2
Reaction score
0
Hello there, I'm having trouble proving this by induction

Homework Statement


\frac{1}{1(2)} + 1\frac{1}{2(3)}+...+\frac{1}{n(n+1)} = \frac{n}{n+1}


Homework Equations


For the base case n=1

\frac{1}{1(2)}=\frac{1}{1+1} = \frac{1}{2} = \frac{1}{2}

\frac{k}{k+1} + \frac{1}{(k+1)(k+2)} <- the second term would be the next integer

The Attempt at a Solution


\frac{1}{1(2)}+ \frac{1}{2(3)}+\frac{1}{k(k+1)} + \frac{1}{(k+1)(k+2)} = \frac{k+1}{(k+1)+1} = \frac{k}{k+2} + \frac{1}{k+2}

I don't know where to go from here, any help would be appreciated
 
Physics news on Phys.org
welcome to pf!

hi welcome to pf! :wink:
thefeedinghan said:
\frac{k}{k+1} + \frac{1}{(k+1)(k+2)}

ok, now put the whole thing over (k+1)(k+2) …

what do you get? :smile:
 
oh, thanks very much! was pretty obvious now!
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
Back
Top