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# Need help!!!

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Hello,

I 'd appreciate help with the below questions :)

1. 2. 3. Mar 19, 2019
edited by Guest  Mar 19, 2019

#1
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1.   The common difference is   33......the first term is 20

So.....the formula is for the number sold in the nth week is

20 + 33 ( n - 1)  =

20 + 33n  - 33

33n  - 13

2.     an  =  -2n + 7

First term is   -2(1) + 7  =  5

Second term is   -2(2) + 7   =  3

So....the common difference is - 2

So....the recursive rule is   an  = an-1 - 2

So.....

a1 = 5       an  = an-1 - 2

3.  2, 9, 16, 23 , 30

The common difference is  7

The first term is  2

So....the explicit formula for the nth term is

an =  2 + 7 ( n - 1)  =  2 + 7n - 7   =  -5 + 7n   Mar 19, 2019
#2
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Thanks, Cphill!

I really struggle with these types of questions, so if you could help with these questions also that would be greatly appreciated!

1st one: 2nd one: Guest Mar 19, 2019
#3
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First one

-2.7, -8.3, -13.9 , -19.5, -25.1

The common difference is    -8.3 - (-2.7) = -5.6

The first term is  -2.7

So....the recursive rule is

an  = an-1 - 5.6   where a1 = -2.7

Second one :

12.5, 11, 9.5.....

The common difference is    11 - 12.5  = -1.5

The first term is  12.5

So....the explicit rule is

an =  a1 - 1.5(n - 1)   =  12.5  - 1.5n + 1.5   =  14 -1.5n   CPhill  Mar 19, 2019