Question

The 8 th term of an A.P is – 23 and its 12 th term is – 39. Find the A.P.

Answer 1

Answer:

-2,-5,-8,-11,-14

Step-by-step explanation:

GIVEN :-

a8 = -23 ——————(1)

a12 = -39 ——————(2)

TO FIND:-

AP

SOLUTION:-

From equation 1:-

a8 = a+7d

ie:- a+7d = -23 ——————(3)

a12 = a+11d

ie:- a+11d= -39 ——————(4)

Subtract equation (3) and (4)

a+7d = -23

a+11d = -39

- - +

_________

0 - 4d = 12

_________

So, we got - 4d = 12

d = 12/-4

d = -3

Put in equation 3,

a + 7d = -23

Put d = -3

a + 7(-3) = -23

a -21 = -23

a = -23 + 21

a = -2

So, a = -2 and d = -3

a2 = a1 + d

a2 = (-2) + (-3)

a2 = -2-3

a2 = -5

Now, a2 = -5 and d = -3

a3 = a2 + d

a3 = -5-3

a3 = -8

So, the AP is = -2 , -5 , -8 , -11 , -14 and so on....

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