-5 is on the left side of zero (negative) and 5 is on the right side of zero (positive). So, 5 is the answer...
for the first term:
n= 1 there is 1 item
n=2 there are 2+1 = 3 items
n = 3 there are 3+2+1 = 3+2 = 6 items
n = 4 there are 4+3+2+1 = 4+6 = 10 items
We are adding the "n" term each time
n = 5 10+5 = 15
n= 6 15+6 = 21
n = 7 21+7 = 28
n = 8 28+8 = 36
There would be 36 items in the 8th step
-15t/2 + 14159/272
I'm not exactly sure what you are looking for, but this is what I got.
The formula can be written in the form ...
... T = (original temperature) + x·(change in temperature each minute)
The problem statement gives you the original temperature (21 °C) and tells you the temperature after 12 minutes. You have to use that information to figure out the change in temperature each minute.
The change in temperature in 12 minutes is (75 °C) - (21 °C) = 54 °C. That is the change in 12 minutes, so the change in 1 minute will be 1/12 of that:
... 54/12 = 4.5
Using this value in the equation for T, we have
... T = 21 + 4.5x
