Geometric Sequence Formulas

Find the common ratio for the geometric sequence:

2, -4, 8, -16, ...

• 2

• -2

• 1/2

• -1/2

Find the common ratio for the geometric sequence:

10, 20, 40, 80, ...

• 10

• 2

• 1/2

• 4

Write the explicit formula for the geometric sequence.

10, 20, 40, 80, ...

• a_n = 10(2)^n-1

• a_n = 10(2)ⁿ

• a_n = 2(10)^n-1

• a_n = 2(10)ⁿ

Find the common ratio for the geometric sequence:

7, -7, 7, -7, ...

• 1

• -7

• 7

• -1

Write the explicit formula for the geometric sequence.

7, -7, 7, -7, ...

• a_n = 7(1)ⁿ

• a_n = 7(-1)^n-1

• a_n = 7(-1)ⁿ

• a_n = -1(7)^n-1

Find the common ratio for the geometric sequence:

3, -12, 48, -192, ...

• -4

• 4

• 1/4

• -1/4

Write the explicit formula for the geometric sequence.

3, -12, 48, -192, ...

• a_n = 4(3)^n-1

• a_n = -4(3)^n-1

• a_n = 3(4)^n-1

• a_n = 3(-4)^n-1

Find the common ratio for the geometric sequence.

162, 108, 72, 48, ...

• 2/3

• 3/2

• -2/3

• -3/2

What is a common ratio?

• same number multiplied constantly

• same number added constantly

Write the explicit formula for the geometric sequence.

162, 108, 72, 48, ...

• a_n = 162(2/3)^n-1

• a_n = 162(3/2)^n-1

• a_n = (2/3)(162)^n-1

• a_n = 162 + (n-1)(-54)