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Find the common difference and the 8th term of the arithmetic progression 7,11,15,19

Sagot :

The common difference is 4.
The 8th term is 35.
In the sequence*) 7 + 4 = 11 + 4 = 15 + 4 = 19 + 4 = 23 + 4 = 27 +4 = 31 + 4 = 35
Common difference: 11-7 = 4
                               15-11 = 4
                                19-15 = 4
Common difference = 4

To solve for any term after 19 in this arithmetic sequence, use the formula:
an = a1 + (n-1) (d)

Looking for 8th term:
n = 8
a1 = 7
d (common difference) =4

a8 = 7 + (8-1) (d)
a8 = 7 + (7)(4)
a8 = 7 + 28
a8 = 35

The 8th term is 35.

(It's very important that you know the formula, so you can solve even the hundredth term of the given arithmetic sequence).