Jika -12,a, b, c, d, e, f, 23 merupakan barisan aritmatika maka a + c + e=....

U1 = -12
U8 = 23
U1 + 7b = 23
-12 + 7b = 23
7b= 23 + 12
7b = 35
b = 5

a = U1 + b = -12 + 5 = -7
b = U1 + 2b = -12 + 10 = -2
e = U1 + 5b = -12 + 25 = 13

a + b + e = -7 + (-2) + 13 = 4