Answer:
-10190
Explanation:
May I tell you how neat your work is? Always go straight down the way you are doing. 1 line, 1 piece of information.
I can give you the answer, but at this point I cannot give you the explicit formula. I will open up this question or rather get a mod to do it when I know how the answer was derived.
The answer is -10190. This was done using a spreadsheet.
I don't think it is worth your time to work out how the explicit formula is derived, but if you really want it, I can put it in the comments. Just leave me a note at the bottom of this answer.
The formula is
tn = -20*2^(n - 1) + 50 So for t10, you would get
t_10 = - 20*2^(10 - 1) + 50
t_10 = -20*2^9 + 50
t_10 = -20*512 + 50
t_10 = -10240 + 50
t_10 = -10190 Which is just what the speadsheet gave.