Arithmetic & Geometric Sequences

Is the sequence arithmetic, geometric, or neither?

2, 5, 11, 20 . . .

• arithmetic

• geometric

• neither

Is the sequence arithmetic, geometric, or neither?

6, -12, 24, -48 . . .

• arithmetic

• geometric

• neither

Create the explicit formula for the sequence:

2, 8, 14, 20, 26 . . .

• a_n= 2 + 6(n-1)

• a_n= 4 + 4(n-1)

• a_n= 4(4)^n-1

• a_n= 2(4)^n-1

Write an explicit equation that models the sequence:

25, 21, 17, 13 . . .

• a_n = 25(-4)^n-1

• a_n = 25 - 4(n-1)

• a_n = 25 + 4 (n-1)

• a_n = 4n + 29

What is the recursive rule for the sequence 11, 22, 44, 88 . . .

• a_n = 2(11)^n-1

• a_n = 11 + 2(n-1)

• a_n = 11(2)^n-1

• a_n = 2a_n-1 given a₁=11

Which formula is used to find the explicit equation for arithmetic sequences?

• a_n = a_n-1 + d

• a_n = a_n-1 * r

• a_n = a₁ (r)^n-1

• a_n = a₁ + d(n-1)

Which formula is used to find the explicit equation for geometric sequences?

• a_n = a_n-1 + d

• a_n = a_n-1 * r

• a_n = a₁ (r)^n-1

• a_n = a₁ + d(n-1)

If a₂₀ = - 4 and the common difference is -1/2, find the fourth term in the sequence.

• 3

• 3.5

• 4

• 4.5