Jawabanmu

2014-05-05T19:45:40+07:00
B = 22-10/7-3 = 3
U3=a+2b
10=a+6
a=4

Sn = 30/2(2.4+29.3)
Sn = 1313
Jawaban paling cerdas!
2014-05-05T19:46:59+07:00
Un = a+(n-1)b

U3 = a+2b = 10
U7 = a+6b = 22
______________ -
-4b = -12
b=3
sekarang cari a-nya..
a+2(3) = 10
a+6=10
a=4

Sn=n÷2 (2a+(n-1)b)
S30= 30÷2 (2(4) + 29(3))
S30= 15(8+87)
S30= 15(95)
S30= 1425
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