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December 18, 2014

December 18, 2014

Posted by **De-Graft** on Saturday, November 6, 2010 at 10:17am.

- maths -
**Reiny**, Saturday, November 6, 2010 at 11:32amterm(13) = a+12d

so a+12d = 27 (equation #1)

term(7) = 3term(2)

a+6d = 3(a+d)

a+6d = 3a + 3d

2a - 3d = 0 (equation #2)

It is easy to solve these two equations, (see if you can get a=3, d=-2)

then use your formula for the sum of 10 terms.

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