Posted by Lana on Tuesday, December 16, 2008 at 9:39pm.
Find the sum of the 50 greatest negative integers.
I'm supposed to find a, d, and t(at)n, but I'm not sure which is which. I think it makes sense for n to equal 50, but apart from that, I don't know what else to do. I would really appreciate some sort of explanation on how to solve this. Thank you. Oh, and I have a test on this tomorrow, so I really need the help. :)

Functions  Reiny, Tuesday, December 16, 2008 at 9:50pm
you are simply asked to find
(50) + (49) + ... + (2) + (1)
there are 50 of these, so n=50
the first term is 50, so a=50
the common difference is 1, so d=1
S_{50} = 50/2(50 + (1) = 1275
I was using S(n) = n/2(first + last)
You could have used
S(n) = n/2[2a + (n1)d]
= 25[100 + 49]
= 1275
notice if you had added up the first 50 positive integers you would get +1275 
Functions  Lana, Tuesday, December 16, 2008 at 10:15pm
oh! a = 50?!
for some reason I thought it was 1, but it makes much more sense now. Okay, yeah, I see what you mean. :) Thank you so very much for helping me! :D