Tentukan beda dari suaty deret aritmetika jika diketahui: 1. U1=10 dan U6=5 2. U3=-3 dan U12=-30

1. Un = a + (n-1)b
U1 = a + (1-1)b
10 = a + 0
10 = a

U6 = a + (6-1)b
5 = a + 5b

a + 5b = 5
10 + 5b = 5
5b = 5-10
5b = -5
b = -1

2. U3 = -3
a + (3-1)b = -3
a + 4b = -3
a = -3 - 4b

U12 = -30
a + (12-1)b = -30
a + 11b = -30

a + 11b = -30
-3 - 4b + 11b = -30
7b = 27
b = 27/7


Mohon dikoreksi jawabannya,