I am just starting out learning mathematical induction and I got this homework question to prove with induction but I am not managing.
n∑k=11√k≥√n
Perhaps someone can help me out I don't understand how to move forward from here:
n+1∑k=11√k+1√n+1≥√n+1
proof and explanation would greatly be appreciated :)
Thanks :)
EDIT sorry meant GE not = fixed :)
Answer
If you wanted to prove that
n∑k=11√k≥√n,
that I can do. It is clear for n=1 (since we have equality then), so that it suffices to verify that
n+1∑k=11√k≥√n+1
but this is equivalent to
n∑k=11√k+1√n+1≥√n+1
and again equivalent to
n∑k=1√n+1√k+1≥n+1
so we only need to prove the last statement now, using induction hypothesis. Since
n∑k=11√k≥√n,
we have
n∑k=1√n+1√k≥√n+1√n≥√n√n=n.
Adding the 1's on both sides we get what we wanted.
Hope that helps,
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