jika 1+3+5+7+9......k=625, maka k=....

jawab

a = 1
b = 2

k =2n - 1

sn = 625
n/2 ( a + un) = 625
n( 1+ 2n -1) = 1.250
n(2n) = 1.250
2n² =1250
n²= 625
n = 25

K= 2n- 1
n = 25
K = 2(25) - 1
K = 49