SOLUTION: In an arithmetic sequence the first term is -12 and the 15th term is 135. Find the common difference d.

Question 922689: In an arithmetic sequence the first term is -12 and the 15th term is 135. Find the common difference d.
Answer by srinivas.g(540) (Show Source): You can put this solution on YOUR website!
First term (a)= -12
15 th term = 135
formula for n th term =a+(n-1)*d
where n = no of term
d= common difference
but 15 th term = 135
so 135 = a+(n-1)*d
135 = -12+(15-1)*d
135 = -12+14*d
add 12 on both sides
135+12 = -12+14*d +12
147=14d
divide with 14 on both sides

10.5=d
common difference (d)= 10.5
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