Jawabanmu

2014-02-09T22:10:11+07:00
Rumus Deret : SN =  \frac{n}{2} ( 2a + ( n - 1 ) b )
S2745 =  \frac{15}{2} ( 2a + ( 15 - 1 ) 25 )
 \frac{15}{2} ( 2a + (14) 25 )
 \frac{15}{2} ( 2a + 350 )
= 15 ( 2a + 175 )
S2745 = 30a + 2625 atau
2625 + 30a = S2745
30a = 2745 - 2625
30a = 120
a=120 ÷ 30
a = 40