Question

In an AP if the common difference (d)=-20 and the seventh term (a7) is 4 then find the first term.​

Answer 1

Step-by-step explanation:

Given-

d = -20

a7 = 4

We know that nth term of AP is

=> an = a + (n - 1)d

=> a7 = a + (7 - 1)d [n=7]

=> 4 = a + 6(d)

=> 4 = a + 6(-20)

=> 4 = a + (-120)

=> 4 = a - 120

=> a = 4 + 120

=> a = 124

Hence-

First term of AP is 124.