Staar Algebra Arithmetic and Geometric Sequences Writing Rules

In a geometric sequence, a₄ = −9, a₅ = −27, and a₆ = −81. What is the recursive formula for this sequence?

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In a geometric sequence, a₄ = 18, a₅ = 6, and a₆ = 2. What is the explicit formula for this sequence?

• a_n = 2(3)^n-1

• a_n = 18(3)^n-1

• a_n = 18(1/3)^n-1

• a_n = 486(1/3)^n-1

Arithmetic, geometric, or neither?

4, 9, 14, 19, ...

• Arithmetic

• Geometric

• Neither

Arithmetic, geometric, or neither?

100, 50, 25, 12.5, ...

• Arithmetic

• Geometric

• Neither

Find the common difference:

25, 13, 1, -11, ...

• 12

• -12

• 8

• -8

Find the common ratio:

2, 8, 32, 128, ...

• 1/4

• 4

• 1/6

• 6

Find the next term:

81, 9, 1, 1/9, ...

• 1/81

• 1/27

• 1/18

• 18

Find the explicit formula: 3, 6, 12, 24, ...

• aₙ = 6⋅(½)ⁿ ⁻ ¹

• aₙ = 6⋅(½)ⁿ

• aₙ = 3⋅2ⁿ ⁻ ¹

• aₙ = 3⋅2ⁿ

Find the eighth term:

3, 6, 12, 24, ...

Find the explicit formula:

• aₙ = 6n + 2

• aₙ = 8n + 6

• aₙ = 2n + 6

• aₙ = 6n + 8