#1: a+6d=3
#2: a+11d=-3
subtract them
-5d = 6
d = -6/5
back into a+6d=3
a + 6(-6/5) = 3
a = 3 + 36/5 = 51/5
first three terms are:
51/5 , 9 , 29/5
determine the first three terms of the erithmetic progression of which the 7th term is 3 and the 12th term is -3?
1 answer