Question

if 4th term of an AP is 64 and its 54th term is -61 then find the common difference ?

plz give answer in method

Answer 1

Solution :

Let, the first term of the AP is a and the common difference is d

Then,

4th term = a + (4 - 1) d = a + 3d

or, a + 3d = 64 .....(i)

54th term = a + (54 - 1) d = a + 53d

or, a + 53d = - 61 .....(ii)

Subtracting (i) from (ii), we get

a + 53d - a - 3d = - 61 - 64

or, 50d = - 125

or, d = - 125/50

or, d = - 5/2

or, d = - 2.5

Hence, the common difference is (- 2.5)

Answer 2

Answer:

an=a+(n-1)d

a4=a+3d=64......1

a54=a+53d=-61........2

Sub 1 from 2,

a+53d-a-3d=-61-64

50d=-125

d=-125/50

d=-2.5

Hope it helps u......

Pls mark me as brainliest