Question

In a certain AP, 5 times the 5th term is equal to 8 times the 8th term, then its 13th term is equal to

Answer 1

Step-by-step explanation:

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

5a + 20d = 8a + 56d

5a - 8a = 56d - 20d

-3a = 36d

a= -36d/3

a = -12d

13th term = a+12d

putting value of a

-12d +12d=13th term

13th term= 0

Answer 2

Step-by-step explanation:

$\rm 5T_5=8T_8$

$\rm 5(a+4d)=8(a+7d)$

$\rm 3a+36d=0$

Divide both sides by 3,

$\rm \dfrac{3a}{3}+\dfrac{36d}{3}=0$

$\rm a+12d=0$

$\rm T_{13}=0$