Question

First term of an AP is 4 and the common difference is 3. It's 12 th term is same as the 8 th term of another AP with first term -5. Find the common difference of 2nd AP?

Answer 1

Though SE expects your effort, I give hint so that you can give your 50%50%effort.

Hint:

Given

a3=a1+(3−1)d=−2(1)(1)a3=a1+(3−1)d=−2

and

a21=a1+(21−1)d=70(2)(2)a21=a1+(21−1)d=70

.

So solving these two equation with two unknown a1a1 and dd, leads to answer??

Answer 2

Let first ap

a=4

d=3

t12=a+(n-1)d

T12=4+(12-1)3

=4+11*3

=4+33

=37

For second ap

a= -5

d=?

t8=a+(n-1)d

= -5+(8-1)d

= -5+7d

from condition

t8=t12

-5+7d=37

7d=37+5

7d=42

d=42/7

d=6

so d be 6