Question

How many terms of AP65, 60, 55, -------- are taken so that their Sum is Zero​

Answer 1

Answer:

Step-by-step explanation:

65,60,55 ....

a = 65 , d = -5 , sn = 0

sn = n/2 ( 2a + (n - 1 )d )

0 = n/2 (2 (65) + (n - 1 ) -5)

0 = n/2 (130 -5n + 5 )

0 = n (140 - 5n )

0 = 140n - 5n²

-5n² + 140n = 0

To make the value smaller divide both sides by - 5

n² - 28n = 0

n (n - 28 ) = 0

n - 28 = 0

n = 28