Question

find the sum of first 10 terms of the a.p 15,10,5...

Answer 1

AP - 15,10,5.......

Here

a=15
cd = -5
n= 10

Sum of n terms of AP
$sn = n \div 2(2a + (n - 1)d)$
S10 = 10/2 {2×15+(10-1)-5}

= 5{30+9×-5}

= 5(30-45)

= 5×-15

= -60


Hope it will help you......

Answer 2

I hope this help you Mark as brain list