Question

In the arithmetic progression, a8 = 5, a15 = -23. Find the difference in the progression.

Answer 1

let a is the first term and d is the common difference of AP
use formula ,
an = a + (n -1) d
a8 = a + (8-1)d =5
a+7d = 5 ------(1)

a15 = a + (15-1)d
a + 14d = -23 -------(2)
solve equation (1) and(2)

7d = -23 -5 = -28
d = -4

Answer 2

Hi friend,
ATQ a8=5(given)
       a15=-23(given)
and a8=a+7d
        5=a+7d
        a=5-7d_______________(1)
also,a15= a+14d
       -23=a+14d_____________(2)
put the value of a from eqn (1) to eqn(2), we get
-23=5-7d+14d
-23=5+7d
7d=-28
d=-4
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