Wednesday 15 February 2017

discrete mathematics - Hard Mathematical Induction

I have a mathematical induction question and I know what I need to do just not how to do it.



The question is:




Prove the equality of:



$$(1 + 2 + . . . + n)^2 = 1^3 + 2^3 . . . + n^3$$





Base case:



$$(1 + 2)^2 = 1^3 + 2^3\\
(3)^2 = 1 + 8\\
9 = 9$$



and I understand I have to get the sides to equal each other though I'm not sure how to do that:



I use this:




$$(1 + . . . + n + (n + 1))^2 = 1^3 + . . . + n^3 + (n + 1)^3$$



but i can't seem to factor anything in anyway to figure it out . . .



I've tried putting the $S(n)$ in the $S(n + 1)$:



$$(1 + . . . + n + (n + 1))^2 = (1 + . . . + n)^2 + (n + 1)^3$$



but its just getting the $-(n + 1)^3$ on the first side I can't figure out...




Any help would be amazing!!!!

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