Question

The nth term of an AP is 7-4n. Find its common difference

Answer 1

nth term of an AP = 7 -4n
e.g Tn = 7 -4n
put n = 1 then T1 = 7 - 4= 3
put n = 2 then T2 = 7 -4× 2 = 7-8 = -1

common difference = T2 - T1 = -1 -3 = -4

hence common difference = -4

Answer 2

nth term = an = 7-4n
first term = a1 = 7-4(1) = 7-4 = 3
second term = a2 = 7-4(2) = 7-8 = -1
second term - first term = a2 - a1 = common difference(d)
                                      = -1-3 = -4
Therefore common difference(d) = -4