Geometric Progression Fundamentals

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What is a geometric progression?

A sequence of numbers where each term after the first is found by multiplying the previous one by a fixed, non-zero number called the common ratio.

How is the common ratio in a geometric sequence determined?

By dividing any term by the previous term.

Write the formula for the n-th term of a geometric sequence.

a_n = a_1 * r^(n-1) where a_1 is the first term and r is the common ratio.

What is the sum of the first n terms of a geometric series?

S_n = a * (1 - r^n) / (1 - r) for r ≠ 1.

In a geometric sequence, if the first term is 3 and the common ratio is 2, what is the fourth term?

The fourth term is 3 * 2^3 = 24.

How does a geometric sequence differ from an arithmetic sequence?

In a geometric sequence, each term is multiplied by a constant ratio, whereas in an arithmetic sequence, a constant is added to each term.

What is the common ratio if the sequence is 5, 15, 45?

The common ratio is 15/5 = 3.

Explain what happens if the common ratio is 1.

The sequence remains constant, with each term equal to the first term.

Given the sequence 1, 1/2, 1/4, what is the common ratio?

The common ratio is 1/2.

What is an infinite geometric series?

A geometric series that has an infinite number of terms.

For an infinite geometric series, when does it converge?

It converges when the absolute value of the common ratio is less than 1.

What is the formula for the sum of an infinite geometric series?

S = a / (1 - r) for |r| < 1.

Identify the first term and common ratio of the sequence 10, -20, 40, -80.

First term is 10, common ratio is -2.

If the 6th term of a geometric sequence is 128 and the common ratio is 2, what is the first term?

First term a_1 = 128 / 2^(6-1) = 4.

True or False? The sequence 1/3, 1, 3, 9 is geometric.

True, with a common ratio of 3.





Test Your Knowledge

Select the correct option


1. What is a geometric progression?

A sequence of numbers where each term after the first is found by multiplying the previous one by a fixed, non-zero number called the common ratio.

A sequence where each term is added to the previous one by a constant.

A sequence where each term is subtracted from the previous one by a constant.

A mathematical series where numbers are arranged in increasing order.

2. How is the common ratio in a geometric sequence determined?

By adding the first and last term.

By multiplying any term by the previous term.

By subtracting any term from the previous term.

By dividing any term by the previous term.

3. Write the formula for the n-th term of a geometric sequence.

a_n = a_1 * r^(n-1) where a_1 is the first term and r is the common ratio.

a_n = a_1 * (n-1) + r.

a_n = n * a_1 - r.

a_n = a_1 + r^(n-1).

4. What is the sum of the first n terms of a geometric series?

S_n = a * (1 - r^n) / (1 - r) for r ≠ 1.

S_n = a * n * r.

S_n = a_n + r^n.

S_n = a + r + n.

5. In a geometric sequence, if the first term is 3 and the common ratio is 2, what is the fourth term?

12

24

18

16

6. How does a geometric sequence differ from an arithmetic sequence?

In a geometric sequence, each term is multiplied by a constant ratio, whereas in an arithmetic sequence, a constant is added to each term.

In a geometric sequence, each term is subtracted by a constant, whereas in an arithmetic sequence, a constant is added to each term.

A geometric sequence involves division; an arithmetic sequence involves multiplication.

In a geometric sequence, each term is multiplied by a variable, whereas in an arithmetic sequence, a constant is added.

7. What is the common ratio if the sequence is 5, 15, 45?

5

3

15

9

8. Explain what happens if the common ratio is 1.

The sequence decreases to zero.

The sequence remains constant, with each term equal to the first term.

The sequence alternates between 1 and -1.

The sequence becomes an arithmetic series.

9. Given the sequence 1, 1/2, 1/4, what is the common ratio?

1/2

2

1

1/4

10. What is an infinite geometric series?

A geometric series that has an infinite number of terms.

A geometric series with a finite number of terms.

A sequence with both geometric and arithmetic properties.

A sequence with alternating common ratios.

11. For an infinite geometric series, when does it converge?

When the common ratio is greater than 1.

When the terms increase exponentially.

It converges when the absolute value of the common ratio is less than 1.

It converges if it is finite.

12. What is the formula for the sum of an infinite geometric series?

S = a / (1 - r) for |r| < 1.

S = a * (1 - r)^(n-1).

S = ar^n / (1 - r).

S = a + r + n.

13. Identify the first term and common ratio of the sequence 10, -20, 40, -80.

First term is 10, common ratio is 4.

First term is 10, common ratio is -2.

First term is -10, common ratio is 2.

First term is 20, common ratio is -1.

14. If the 6th term of a geometric sequence is 128 and the common ratio is 2, what is the first term?

First term a_1 = 128 / 2^(6-1) = 4.

First term a_1 = 2 * 128 = 256.

First term a_1 = 32.

First term a_1 = 128 / 6 = 21.33.

15. True or False? The sequence 1/3, 1, 3, 9 is geometric.

True, with a common ratio of 3.

False, with a common difference of 2.

True, with no pattern.

False, it is an arithmetic sequence.