Posted by Watermelon on Thursday, November 24, 2011 at 3:48am.
The sixth term of an Arithmetic Progression is 23 and the sum of the six terms is 78. Find the first term and the common difference.

AP calculus  Steve, Thursday, November 24, 2011 at 5:44am
a+5d = 23
6/2 * [a + (a+5d)] = 78
a + 5d = 23
6a + 15d = 78
a=3
d=4
sequence: 3 7 11 15 19 23
sum: 78

AP calculus  Watermelon, Thursday, November 24, 2011 at 7:03am
Given an arithmetic progression 7,3,1,..., state three consecutive terms in this progression which sum up to 75.

AP calculus  Steve, Thursday, November 24, 2011 at 7:03pm
The kth term is a+(k1)d
so you want
3a + (k1 + k + k+1)d = 75
3(7) + 3k(4) = 75
12k = 96
k=8
So, the 8th,9th,10th terms are
21,25,29 add up to 75

AP calculus  NCaxUXvPLp, Monday, December 12, 2011 at 4:34am
I can already tell that's gonna be super hlepufl.
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