Having problems with another inductive proof.. again with the algebra
$$\sum_{k=1}^n \frac{1}{\sqrt{k}}>\sqrt{n} :\ \forall n\in\mathbb{N}, n>1$$
What I've done:
- Proved for n=1
- Showed I need to prove $$\sum_{k=1}^{n+1} \frac{1}{\sqrt{k}}>\sqrt{n+1}$$
- Attempt: $$\sum_{k=1}^{n} \frac{1}{\sqrt{k}}+\frac{1}{\sqrt{n+1}}>\sqrt{n}+\frac{1}{\sqrt{n+1}}$$ $$\iff \sum_{k=1}^{n+1} \frac{1}{\sqrt{k}}>\sqrt{n}+\frac{1}{\sqrt{n+1}} $$
Again, I come no futher than this. I assume its something I don't know or can't see.
Cheers!
Andy
Edit: After being referred to another similar question, what I don't understand is why $$\sqrt{n}+\frac{1}{\sqrt{n+1}}>\sqrt{n+1}$$ which it obviously must be.
In the same vein, during my proof I didn't know (algebraically) to prove $$\sum_{k=1}^n \frac{1}{\sqrt{k}}>\sqrt{n}$$
If I put numbers in I can see that it is trivially true but not why it is generally true..