Question

In an AP, if the common difference (d) =-4, and the seventh term (a7) is 4, then find the first term.

Answer 1

first term is 28
a+6d=4
a+6*-4=4
a-24=4
a=28

Answer 2

d = -4
a7 = 4
n = 7
                             a7 = a + (n - 1) d
                               4 = a + 6d
                               4 = a + (-24)
                               a = 28