MATH
posted by lYDIA on .
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+(n1)d?
If so, what would my "n" by in the equation?

The nth term of an arithmetic progression is defined by N = a + (n1)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) = ? 
402

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