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ALGEBRA Help! Anymore?
Find the arithmetic mean an of the given terms.
a(n-1) = -21, a(n+1) = -7
2 Answers
- Anonymous1 decade agoFavorite Answer
Solve for a for each expression:
a = -21/(n - 1) and a = -7/(n + 1)
Then,
-7/(n + 1) = -21/(n - 1)
-7(n - 1) = -21(n + 1)
n - 1 = 3(n + 1)
n - 1 = 3n + 3
-1 - 3 = 3n + n
-4 = 4n
n = -1
Then,
-(n - 1) = -21
n - 1 = 21
n = 22
I hope this helps!
Source(s): Knowledge - 1 decade ago
a(n-1) = -21 ---------------> a = -21 / (n-1)
a(n+1) = -7
[-21 / (n-1) ] * (n+1) = -7
- 21 (n+1) = -7 (n-1)
21 n + 21 = 7n - 7
14 n = -28
n = -2
a = -21 / (n-1) = -21 / -3 = 7
n = -2
a = 7
