Question

If 8th term of an AP is -23 and its 12th term -39. Find the AP?

Answer 1

a8 = -23
a12 = -39

a+7d = -23. (sign changed)
a+11d = -39
--------------------
-4d = 16
d = -4

a+7d = -23
a+7x(-4) = -23
a= -23+28
= 5

a = 5
a2 = a+d = 5+(-4) = 1
a3 = a+2d = 5+2x(-4) = 5+(-8) = -3


A.P is 5,1,3...................an



HOPE IT HELPS YOU !!!!

Answer 2

Hey there !!

Given :-

→ a₈ = -23.

→a₁₂ = -39.

To find :-

→ AP.

Solution :-

We have ,

→ a₈ = -23.

⇒ a + 7d = -23.........(1).

And,

→ a₁₂ = -39.

⇒ a + 11d = -39......(2).

On substracting equation (1) and  (2), we get

a + 7d = -23.

a + 11d = -39.

-  -         +

___________

⇒ -4d = 16.

⇒ d = 16/-4= -4.

Put the value of d in equation (1), we get

⇒ a + 7d = -23.

⇒ a + 7 × (-4) = -23.

⇒ a - 28 = -23.

⇒ a = -23 + 28.

⇒ a₁ = 5 .

⇒ a₂ = 5 - 4= 1.

⇒ a₃ = 1 - 4 = -3.

Hence, AP is 5, 1, -3.... .

THANKS

#BeBrainly.