# Thread: how to prove the induction problem

1. ## how to prove the induction problem

4+8+12+...+4n= 2n(n+1)

2. ## Re: how to prove the induction problem

Originally Posted by yingao
4+8+12+...+4n= 2n(n+1)
Can you show that it is true for $n=1~?$

3. ## Re: how to prove the induction problem

4n= 2n(n+1)

4 x1 = 2x1 (1+1)

4 = 4

4. ## Re: how to prove the induction problem

Originally Posted by yingao
4n= 2n(n+1)
4 x1 = 2x1 (1+1)
4 = 4
O.K.
Now if we know that for K>1, 4+8+12+...+4K= 2K(K+1) what can say about 4+8+12+...+4K+4(K+1)?

5. ## Re: how to prove the induction problem

Thanks for your help! I don't know how to go on from here.