• Math help needed
    11 replies, posted
Can anyone help me find the algebraic formula for the following number sequence: 10,20,40,70,110,160,220,290,370.....
oh seriously, it's too fucking hard to do it we aren't your math teacher
I prefer these kind of problems where you can just give the final number. But then I always hated mathematics.
wait a sec
the sum of what?
term n+1 = term(n) + n*10 I'll try figure it out just in terms of algebra (as in, the term not in terms of the term before it, but kind of like an arithmetic, or geometric progression), I'm not sure what is the proper way you are meant to do these.
Btw, the first term is 0,not 1
term n = 10n^2 - 5n(1+n) wait something went wrong
nth term = 5(n^2 - n + 2) That's according to: [url]http://www.wolframalpha.com/input/?i=10,20,40,70,110,160,220,290,370[/url]
Wait, I just had to add 10 and it's the same as that :( If you wanna use the way I did it, which is probably long and shit, term n+1 = term(n) + n*10 now term n = term (n-1) + (n-1)*10 term n-1 = term (n-2) + (n-2)*10 ect all the way to term 1 = 10 get term n+1 in terms of all this shit to term 1 term n+1 = term 1 + 10(n+(n-1)+(n-2)+......all the way to (n-n) since there are n lots of n added together it is nxn = n^2 term n+1 = term 1 + 10(n^2-(1+2+3+.....n)) =term1 + 10(n^2 - n/2(1+n)) (sum of arithmetic series) = 10 + 10(n^2-n/2 - n^2/2) (term 1 = 10) =10 + 5n^2 - 5n = 5(n^2-n+2)
thanks it worked
my brain hurts after readomg thos thread
Sorry, you need to Log In to post a reply to this thread.