Question

if the third term and 9th term of an ap are 4 and -8 respectively then which term of the ap is zero​

Answer 1

Answer:

Thus the fifth term of the ap is 0

Answer 2

Answer:

• a(3) = a+2d
• 4 = a+2d

• a(9) = a+8d
• -8 = a+8d

• (elimination method)-
• a+2d = 4

(-)a+(-)8d =(+) -8 (opposite sign)

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0 -6d = 12

d = -2

• a+2(-2) = 4 (substitution)
• a = 8

• a(n) = a + (n-1)d
• 0 = 8+(n-1)(-2)

= 8 - 2n + 2

= 10 - 2n

2n=10

n = 5