Here's the question you clicked on:
NatalieLove
What is the sum of the arithmetic sequence 137, 125, 113 …, if there are 38 terms?
Do you see that the numbers are increasing by 8?
i would do it the old school way and keep subtracting 12 until you get 38 terms, then add lol
\[\sum_{i=0}^{37}(137+8i)=137+8(0)+\sum_{i=1}^{37}(137+8i)\] Now use \[\sum_{i=1}^{n}i=\frac{n(n+1)}{2} \text{ and } \sum_{i=1}^{n}c=cn\]
Im still not getting the correct answer
whay are people using d=8
i dont know im gonna guess
Whenever you need to find the sum of an arithmetic series use this formula: \[ \frac n 2 \left( 2a+ (n-1) \right)\times d) \tag{1}\] a= first term n= number of terms d= common difference Here, \(n= 38, a = 137 \) and \( d = -12\). Substituting these in \((1)\), and assuming my algebra is right you answer should be \(-3230 \)
I know but the answer does not show up in the multiple choose
@NatalieLove: Revert if you need help in proving that formula.
We are doing the same steps the test its incorrect. It does not show up as a choose Thank You
omg lol I said increasing by 8 and then continue to think the thingy was increasing by 8 sometimes i wonder about myself lol