Question

 If the 3rd and the 9th terms of an A.P. are 4 and − 8 respectively, then which term of this A.P is zero.​

Answer 1

Answer:

5th

Step-by-step explanation:

Given -

• 3rd term of ap = 4

a + 2d = 4

• 9th term of ap = -8

a + 8d = -8

• a(n) = 0

To find -

• Which term of this A.P is zero

Solution-

• a + 2d = 4-----------1
• a + 8d = -8----------2

→ now, 1 - 2

→ -6d = 12

d = -2 (putting in 1)

→ a + 2(-2) = 4

a -4 = 4

a = 4 + 4

a = 8

→ a(n) = 0

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

0 = 8 + (n - 1)(-2)

-8 = -2n + 2

-8 - 2 = -2n

-10 = -2n

-10/-2 = n

5 = n

therefore , 5th term of the ap will be 0

Answer 2

Answer:

n = 5

Step-by-step explanation:

5th term of the ap will be 0