I'm working on some algebra 2 homework and I got this problem for number 51: Find a1 for each
Sn = -2912, r = 3, n = 6. I plugged this into the formula to get 2912 = a1 - a1(792)/2 and then multiplied the 2 to get 5824 = a1-a1(729), what do I do from here?

Question

I'm working on some algebra 2 homework and I got this problem for number 51: Find a1 for each
Sn = -2912, r = 3, n = 6. I plugged this into the formula to get 2912 = a1 - a1(792)/2 and then multiplied the 2 to get 5824 = a1-a1(729),  what do I do from here?

jim_thompson5910 · Answer

Make sure you fix the 792 and change it to 729

jim_thompson5910 · Answer

if it helps, think of a1 as x

so you'd have 5824 = x - x*729

christianx2 · Answer

But then I would I do 5824/729 and get 7.989 = x - x and then 7.989=0

jim_thompson5910 · Answer

what would x - x*729 simplify to?

jim_thompson5910 · Answer

hints

x = 1x
x*729 = 729x

christianx2 · Answer

OOOOhhhhhhh I see it now

christianx2 · Answer

728x?

jim_thompson5910 · Answer

small - big = negative number

jim_thompson5910 · Answer

1-729 = -728

christianx2 · Answer

Ok so -728x = 5824? then 5824/-728 = -8 = a1 right?

jim_thompson5910 · Answer

yep the first term is $\Large a_1 = {\color{red}{-8}}$

christianx2 · Answer

Ok I got it now. Thanks for your help Jim.

jim_thompson5910 · Answer

you're welcome