Question

the sum of first 15 terms of the A.P -1,-12,-14,-16,.....is......​

Answer 1

Answer:

-1080

Step-by-step explanation:

A.P= 1,-12,-14,-16,.....

a= -1

d= -12- (-1) = -12+1

= -11

n=15

Sum of n terms of A.P = n/2[2a + (n-1)*d]

Sum of 15 terms = 15/2[2(-1) + (15-1)*-11]

= 15/2[-2 + 14*-11]

= 15/2 [-2 -154]

= 15/2[-156]

= 15[-72]

Sum of 15 terms = - 1080

HOPE YOU UNDERSTOOD THE SOLUTION