Find the first four terms in the sequence an=15+6n.

A. 18, 12, 6, 0

B. 20, 26, 32, 38

C. 21, 27, 33, 39

D. 20, 14, 8, 2

The first four terms in the sequence an=15+6n are 21, 27, 33, and 39.

The correct option is C. 21, 27, 33, 39

From the question, the equation to calculate the nth term is given which is

an=15+6n.

Now, let a1, a2, a3 and a4 denote the first, second, third and fourth terms respectively.

For the first term, a1

n = 1,

From the given equation, an=15+6n

∴ a1 = 15 + 6(1)

a1 = 15 + 6

a1 = 21

∴The first term is 21

For the second term, a2

n = 2,

From the given equation, an=15+6n

∴ a2 = 15 + 6(2)

a2 = 15 + 12

a2 = 27

∴The second term is 27

For the third term, a3

n = 3,

From the given equation, an=15+6n

∴ a3 = 15 + 6(3)

a3 = 15 + 18

a3 = 33

∴The third term is 33

For the fourth term, a4

n = 4,

From the given equation, an=15+6n

∴ a4 = 15 + 6(4)

a4 = 15 + 24

a4 = 39

∴The fourth term is 39

Hence, the first four terms in the sequence an=15+6n are 21, 27, 33, and 39.

The correct option is C. 21, 27, 33, 39

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