Question

Jumlah suku suku deret bilangan ganjil 3+5+7+...+K= 400, maka nilai K=.....

Answer 1

Sn = n/2(6 + (n - 1)2) = 399
n/2(6 + 2n - 2) = 399
n/2(2n + 4) = 399
n² + 2n = 399
n = 19
S19 = 19/2(3 + K) = 399
3 + K = 399 . 2/19
3 + K = 42
K = 39