Question

if 5 times the 5th term of an ap is equal to 8 times its 8 term then show that its 13 term is zero

Answer 1

Answer:

Step-by-step explanation:

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Secondary SchoolMath 8+4 pts

If 5 times the 5th term of an AP is equal to 8 times its 8th term, show that the 13th term is zero.

Report by S8iddhikagamichakul 31.01.2017

Answers

maria9

Maria9 Ace

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

Answer:

Step-by-step explanation:

A/Q

5th term =a+4d

8th term =a+7d

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

5a+20d=8a+56d

3a+36d=0

3(a+12d)=0

a+12d=0

13th term = a+12d

Proved