Asked by Wawa

The fourth term of an arithmetic sequence is less than the fifth term by 3. The seventh term is three times the fifth term. Find the common difference and the first term
Answered by Reiny
just translate and use your definitions of an AS
a+3d = a+4d - 3
d = 3, hey, we got the common difference already

a+6d = 3(a+4d)
a + 6d = 3a + 12d
-2a = 6d = 18
a = -9

check:
terms are:
-9 -6 -3 0 3 6 9 12 15 ....
all conditions check out.
Answered by Muiz
20
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