Posted by **Aliza** on Monday, January 21, 2013 at 5:16am.

Find the no. of terms

1. 3,5,7...33

2.-5,-1,3,...75

Solve each problem.

1. In the Arithmetic sequence 5,8,11,14.... what is n if a sub n is 32?

2.Find the sum of the first 20 terms of the arithmetic sequence -15,-7,31,43...

- Math -
**Reiny**, Monday, January 21, 2013 at 10:34am
1. term(n) = a+(n-1)d

you have a = 3, d = 2 , n = ??

33 = 3 + (n-1)(2)

30 = 2n - 2

28 = 2n

n = 14 ------ there are 14 terms

do the 2nd one the same way

for the other two, I don't know how you defined a sub n

for the last:

first find the number of terms in the same way I showed you

you have a = -15 , d = 12 , n = ?

once you find a and d

use

Sum(n) = (n/2)(2a + (n-1)(d) )

- Math -
**Anonymous**, Tuesday, January 22, 2013 at 6:52am
Thank you so much . 1. In the Arithmetic sequence 5,8,11,14.... what is n if an is 32?

1. In the Arithmetic sequence 5,8,11,14.... what is n if n is 32?

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