s5 = 70 dan j3 = 462 hitunglah (a) a (b) b (c) s12 (d) j10

S5 = 70
a + 4b = 70 .... a = 70 - 4b (persamaan 1)

J3 = 462 ...................................... Jn = n/2(2a + (n - 1)b)
3/2(2a + (3 - 1)b) = 462
3(2a + 2b) = 924
a + b = 154 (persamaan 2)
 
a + b = 154
(70 - 4b) + b = 154
-3b = 84
b = - 28

a = 70 - 4b
a = 70 - 4. (-28)
a = 70 + 112
a = 182

S12 = a + 11b
       = 182 + 11. (-28)
       = - 126

J10 = 10/2 ( 2. 182 + 9. (-28))
       = 5( 364 - 252)
       = 5 (112)
       = 560