Question

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

Answer 1

a+(n-1)d=4
a+(7-1)-4=4
a+-24=4
a=28
therefore first number is 28
hope you will understand

Answer 2

Hi there!

Given,
Common difference, d = -4

$a_n$ = a + (n - 1) d

Also Given that,
$a_7$ = 4

a + (7 - 1) × (-4) = 4

a + 6 × (-4) = 4

a - 24 = 4

a = 24 + 4

a = 28

Hence,
First term, a = 28

Hope it helps! :D