My Math Forum Arithmetic Progression exercise

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 June 7th, 2017, 12:38 PM #1 Newbie   Joined: Dec 2016 From: Argentina Posts: 5 Thanks: 0 Arithmetic Progression exercise Hi guys, I have a very important exam very soon and this is one of the examples. No idea how to do this one, can you help me? Assume that a, b and c are consecutive terms of an arithmetic progression (a
 June 7th, 2017, 01:35 PM #2 Math Team   Joined: Jul 2011 From: Texas Posts: 2,737 Thanks: 1387 $a + (a+d) + (a+2d) = 24$ $a(a+d)(a+2d) = 440$ solve the system of equations for $a$ and the common difference of the arithmetic progression, $d$ Thanks from jonah and Asami
 June 7th, 2017, 01:36 PM #3 Senior Member     Joined: Mar 2011 From: Chicago, IL Posts: 214 Thanks: 77 b=a+d, c=a+2d where d is a difference of the arithmetic progression. a+b+c=3a+3d=24 => a+d=b=8 abc=(8-d)8(8+d)=440 => (8-d)(8+d)=55 => d=3 a, b, c = 5, 8, 11 Thanks from Asami
 June 7th, 2017, 04:23 PM #4 Newbie   Joined: Dec 2016 From: Argentina Posts: 5 Thanks: 0 Thank you for the help guys! But the truth is that I don't understand what you did, what is that D there doing what?
June 7th, 2017, 08:10 PM   #5
Math Team

Joined: Jul 2011
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Quote:
 Originally Posted by Asami Thank you for the help guys! But the truth is that I don't understand what you did, what is that D there doing what?
An arithmetic progression is a sequence of numbers that have a common difference between each consecutive pair of terms (that would be the $d$).

examples ...

1, 4, 7, 10, ... note $d=3$

14, 9, 4, -1, ... note $d=-5$

x, x-2a, x-4a, x-6a, ...
so, what is the common difference, $d$, of this progression?

Recommend you visit the link ...

arithmetic sequences & sums

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