Hi,

arithmetic sequence 8, 14, 20 … : d = 6

 





 

Answer by richwmiller(17219)   (Show Source): You can put this solution on YOUR website!
 How can we tell you what you did wrong, if you don't show us what you did?

S = ½(2a + (n-1)d)n

S = ½(2*8 + (21)6)22

S = 1562



or another way

Find a22

an = a + (n - 1)d

a22 = 8 + (21)6

a22=134

now find the sum

S = ½(a + an)n

S = ½(8 + 134)22

S = 11(142)

s=1562





 

Answer by Edwin McCravy(20055)   (Show Source): You can put this solution on YOUR website!
 
You can also use the other formula:



8, 14, 20 …, if there are 22 terms

 = the first term which = 8

d = common difference = 2nd term - 1st term = 14 - 8 = 6

check d:

d = common difference = 3rd term - 2nd term = 20 - 14 = 6

So d = 6

n = the number of terms = 22

Substitute , , and 

















Edwin



 

Answer by AnlytcPhil(1806)   (Show Source): You can put this solution on YOUR website!
 Question 856145

You can also use the other formula:



8, 14, 20 …, if there are 22 terms

 = the first term which = 8

d = common difference = 2nd term - 1st term = 14 - 8 = 6

check d:

d = common difference = 3rd term - 2nd term = 20 - 14 = 6

So d = 6

n = the number of terms = 22

Substitute , , and 














Edwin





 

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