Pelajaran mtk kls 8 aritmatika Dik:U5=19 U7=27 Dit: a) suku pertama b) tentukan beda c) suku ke-20 d) 5 suju pertama dari barisan itu Tolong bantu jawab yaa! Te

u5 = 19
a + 4b = 19

u7 = 27
a + 6b = 27

a + 4b = 19
a + 6b = 27
-2b = -8
b = 4

a) a + 4b = 19
    a + 4 . 4 = 19
    a = 19 - 16 = 3
b) b = 4
c) u20 = a + 19b = 3 + 19 . 4 = 3 + 76 = 79
d) s5 = n/2 (2a + 4b) = 5/2 (2 . 3 + 4. 4) = 5/2 . 22 = 55

cara cepat cari beda
u7-u5 / 7-5 = 27-19 / 2 = 8/2 = 4

19 = a + (5-1) 4
19 = a + 16
3 = a

3,7,11,15,19,23,27,31,.....

u20 = 3 + (20-1) 4 = 3 + 76 = 79