Question

if 5 times the 5term of an AP is equal to 8 times its 8term, show that it's 13term is 0

Answer 1

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

(proved)

Answer 2

Hey mate ☺️

See the attachment☺️

Hope it helps you ☺️✌️✌️