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April 25, 2014

Posted by **JOSHUA BAME** on Friday, November 26, 2010 at 5:41am.

IF THE DIFFERENCE BETWEEN THE 6TH AND 3RD TERM IS 12,

FIND THE:

COMMON DIFFERENCE,

1ST TERM,

20TH TERM.

- arithmetic progression -
**MathMate**, Friday, November 26, 2010 at 7:55amLet

d = the common difference

t(n)=nth term

t(6)-t(5)=d

t(5)-t(4)=d

t(4)-t(3)=d

Add

t(6)-t(3)=3d

or

3d=12

Solve for the common difference d=4

Sum of the 2nd and 5th terms = 42

t(2)+t(5)

=t(2)+(t(2)+3d)

=2*t(2)+12 = 42

Solve for t(2) = 15

t(1) should be t(2)-1=15-4=11

and

t(20)=t(1)+19d

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