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.


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Answer 1

Answer:

according to the question

3rd term i.e, a + 2d = 4. equation 1

9th term i.e, a + 8d = -8. equation 2

from equation 1 and 2

d = -2

a = 8

so the A.P will be

a = 8

a + d = 6

a + 2d = 4

a + 3d = 2

a + 4d = 0

hence the fourth term will be 0

hope it helps you...

Answer 2

Answer:

a

n

=a+(n−1)d

a

3

=4=a+2d ....(1)

a

9

=−8=a+8d ....(2)

∴4−2d=−8d−8

−2d+8d=−8−4

6d=−12

d=−2

a=4−2d

=4+4=8

a

n

=0,a=8,d=−2

0=8+(n−1)×(−2)

0=8−2n+2

2n=10

n=5

Explanation:

Lelo answer ....