Asked by Haise

find the first and the 15 ters of an arithmetic sequence whose fifth term is -1 and ninth term is 11.
Answered by Ms. Sue
The difference between the consecutive terms is 3.
Answered by Reiny
fifth term = a + 4d = -1
ninth term = a + 8d = 11
subtract them:
4d = 12
d = 3, as Ms. Sue stated
plug back into a + 4d = -1
a + 12 = -1
a = -13 <--- first temr

now use your formulas to find the 15th term.