Jawabanmu

2014-02-26T19:37:37+07:00
Saya hanya tau yang no. 1 a= 80 b= -10 U11=a+10b =80+10(-10) =80+(-100)= -20 U12=a+11b =80+11(-10) =80+(-110)= -30
2014-02-26T20:47:19+07:00
No 2. un=4n+5 u1 = 4+5 =9 u2 = 8+5=13 u3= 12+5=17 s12= 1/2 n (2a + (n-1) b) = 6 (18+11 (4) =6 (62) =372