Question

If 5times the fifth term of an ap is equal to 8times its eighth term, show that its 13th term is zero

Answer 1

Given,

5 (A5) = 8 (A8)

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

So, 5a + 20d = 8a + 56d

3a + 36d = 0

So, a + 12d = 0

Hence, a + (13-1)d = 0


Finally, A13 is 0....


Comment in case of any queries

Answer 2

Answer:

Step-by-step explanation:

Let of the AP

first term= a

common difference=d

ATQ

5[a+(5-1)d]=8[a+(8-1)d]

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

5a + 20d = 8a + 56d

3a = 36d

a= -12d

Now 13th term

a+(13-1)d

=-12d+12d

=0