Thursday, 23 November 2017

discrete mathematics - Finding a formula to sum natural numbers up to n










I got this question in homework:




Find an expression for the sum ‫‪




k=1++n.




and prove it using an induction.



I'm not even near finding the expression. What I did notice is that
if n is (for example) 5 then the sum would be




5242+3222+12



So the first number is always positive and from there on the sign changes.



Any tips on how do I contintue from this point on, assuming I'm in the right direction?



Thanks!


Answer



Hint.

1+2+3+4++n+n+n1+n2+n3++1n+1+n+1+n+1+n+1++n+1


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