Tolong bantu jawab yg b,c,d

Barisan Aritmatika

Un = a + (n – 1)b

U1 + U3 + U5 = 30

a + a + 2b + a + 4b = 30

3a + 6b = 30

a + 2b = 10 … (1)

U2 + U4 + U6 = 39

a + b + a + 3b + a + 5b = 39

3a + 9b = 39

a + 3b = 13 … (2)

kurangkan (2) dan (1)

a + 3b = 13

a + 2b = 10

Kurangkan

b = 3

a + 3b = 13

a = 13 – 3(3)

a = 13 – 9

a = 4

U51 = a + 50b = 4 + 150 = 154

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