Jawabanmu

2014-02-21T10:35:08+07:00
Sn= 1/2 n (a+Un)
670= 1/2 20 (5+n)
670=10 (5+n)
670 = 50 + 10n
670-50 = 10n
620 = 10n
n = 620/10
n= 62
Jawaban q kayak gini, maaf lo salah..
2014-02-21T12:28:02+07:00
Sn= 1/2 n (a+Un)
670= 1/2 20 (5+n)
670=10 (5+n)
670 = 50 + 10n
670-50 = 10n
620 = 10n
n = 620/10
n= 62

maaf klo salah