Question

if 5 times the 5th term of an ap is equal to 8 times the 8th term of an ap . prove that the 13th term is zero​

Answer 1

Answer:

5 a5 = 8 a8

5(a +4d) = 8( a+ 7d)

5a + 20d = 8a + 56d

-3a = 36d

a = -12

a13 = a+ 12d

0 = -12 +12d

12d = 12

d = 1

a13 = a+12d

a13 = -12 +12*1

a13 = 0