Posted by **lYDIA** on Sunday, January 16, 2011 at 12:06am.

In an arithmetic sequence, the first term is 100 and the sixth term is 85. Find the common difference. Then, find the 50th term of the sequence.

Do I use the formula an=a1+(n-1)d?

If so, what would my "n" by in the equation?

- MATH -
**tchrwill**, Sunday, January 16, 2011 at 9:28am
The nth term of an arithmetic progression is defined by N = a + (n-1)d where N = the nth term, a = the first term and d = the common difference.

Therefore,

85 = 100 + (6 - 1)d

-15 = 5d making d = -3

The 50th term then becomes

N(50) = 85 + (50 - 1)(-3) = ?

- MATH -
**Bri**, Sunday, January 23, 2011 at 4:38pm
-402

- MATH -
**la**, Friday, January 28, 2011 at 3:45pm
ah what!!!!!!!!!!!!!!!!!!!

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