C2 Help, sum of arithmetic sequences?!!
Un=12-0.5n
so U15=7
15
Σ
n=10
the formula is 0.5n[2a+(n-1)d]
the correct answer is 34.5, how the hell do I get there?
any help would be MASSIVELY appreciated
so U15=7
15
Σ
n=10
the formula is 0.5n[2a+(n-1)d]
the correct answer is 34.5, how the hell do I get there?
any help would be MASSIVELY appreciated
You need to find the sum of the terms 10-15.
First find the sum of the first 15 numbers using the formula.
Then find the sum of the first 10 numbers using the formula.
Subtract the sums and you should get the sum of the terms between 10-15.
There's probably an easier way, but that's how I'd go about doing it.
First find the sum of the first 15 numbers using the formula.
Then find the sum of the first 10 numbers using the formula.
Subtract the sums and you should get the sum of the terms between 10-15.
There's probably an easier way, but that's how I'd go about doing it.
Original post by Trainz
You need to find the sum of the terms 10-15.
First find the sum of the first 15 numbers using the formula.
Then find the sum of the first 10 numbers using the formula.
Subtract the sums and you should get the sum of the terms between 10-15.
There's probably an easier way, but that's how I'd go about doing it.
First find the sum of the first 15 numbers using the formula.
Then find the sum of the first 10 numbers using the formula.
Subtract the sums and you should get the sum of the terms between 10-15.
There's probably an easier way, but that's how I'd go about doing it.
I didn't think of that, thanks a lot
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