Question

find n of the sum of n items of ap 48, 45, 42, ....... is 408​

Answer 1

the answer is 121 pls follow me

Answer 2

Answer:

{ 99 ± √-1191} /6

Step-by-step explanation:

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

408 = n/2 { 2×48+ (n-1) (-3) }

916 = n { 96 -3n +3 }

916 = n { 99 -3n }

3n^2 -99n + 916 = 0

n = { 99 ± √ 9801 - 10,992 } / 6

n = { 99 ± √ -1191} /6