Question

two APs have the same common difference .the first term of one of these is -1 and that of the other is -8 .what is the difference between their 4th terms

Answer 1

let common difference is d

first term of 1 ap is -1

first term of2APIs -8

it's difference of 4term is

(-1+3d)-(-8+3d)

=7+6d

Answer 2

Answer:

7

Step-by-step explanation:

Given,

Common difference in first AP, d = Common difference in second AP, d

a = -1

a' = -8

As we know,

a4 = a+(n-1)d

a4 = -1+(4-1)d

a4 = -1+3d------eq. 1

and,

a'4 = a'+(n-1)d

a'4 = -8+(4-1)d

a'4 = -8+3d--------eq. 2

Subtracting eq. 2 from eq. 1:-

a4 - a'4 = -1+3d-(-8+3d)

a4 - a'4 = -1+3d+8-3d

a4 - a'4 = 8-1

a4 - a'4 = 7

Hence, the difference between 4th term of both APs is 7.

Hope it helps.....