an = a1 + (n-1)d
18 = a1 + (5-1)d
27 = a1 + (8-1)d
so
-9 = -3d
d = 3
then a1 = 18 - 12 = 6
so
an = 6 + (n-1)3
The 5th term and the 8th term of an arithmetic sequence are 18 and 27 respctively.
a)Find the 1st term and the common difference of the arithmetic sequence.
b)Find the general term of the arithmetic sequence.
4 answers
common difference=3,1st term=6and general term=3+3n
13,26,39,52
If a sequence has a first term of 16 and a common difference of -7, what is the 5th and 6th term