Question

What is the value a, if for an A.P., Sn=0, d=-4 and n=13?​

Answer 1

Step-by-step explanation:

$sn = \frac{n}{2} (2a + (n - 1)d)$

$0 = \frac{13}{2} (2a + (13- 1)( - 4))$

0

$0 = \frac{13}{2} (2a +( 12) (- 4 )$

$0 = 2a - 48$

$\frac{48}{2 } = a$

$a = 21$