Question

how many terms of the AP -6,-11/2,-5 .... are needed to give the sum of -25 pls no scam answers

Answer 1

a = -6

d = -11/2 + 6 = 1/2

s = -25

to find ---> n

n/2 {2a+(n-1)d} = -25

n/2 {2×-6 + (n-1)1/2} = -25

n/2 {-12+ n/2 - 1/2} = -25

n/2 {n/2 - 12.5} = -25

n/2(n/2) - n/2(12.5) = -25