Diketahui barisan aritmatika 11,15,19,23,….
carilah u21 dan s21
Dik. a/u1 = 11, b= 4
un= a+(n-1)b
u21= 11 + 20×4 = 11+80 = 91
sn= n/2 (a+un)
s21= 21/2 (11+91) = 21/2 x 102 = 1071
Diketahui barisan aritmatika 11,15,19,23,….
carilah u21 dan s21
Dik. a/u1 = 11, b= 4
un= a+(n-1)b
u21= 11 + 20×4 = 11+80 = 91
sn= n/2 (a+un)
s21= 21/2 (11+91) = 21/2 x 102 = 1071