Gr12 Mathematics: Ch 1.4 Finite Geometric Series
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Questions and Answers

What is the formula for the nth term of a geometric sequence?

  • $$T_n = a \cdot r^n$$
  • $$T_n = a \cdot r^{n-1}$$ (correct)
  • $$T_n = a \cdot r^{n+1}$$
  • $$T_n = a \cdot r^{n-2}$$

What is the purpose of multiplying both sides of the equation by r when deriving the formula for a finite geometric series?

  • To find the common ratio
  • To create a new equation to subtract from the original (correct)
  • To simplify the equation
  • To eliminate the first term

What is the condition for using the alternative formula for a finite geometric series?

  • r < 1
  • r = 1
  • r > 1 (correct)
  • r 1

What is the result of subtracting the second equation from the first when deriving the formula for a finite geometric series?

<p>S_n - rS_n = a - ar^n (D)</p> Signup and view all the answers

What is the general formula for the sum of a finite geometric series?

<p>$$S_n = rac{a(1 - r^n)}{1 - r}$$ (C)</p> Signup and view all the answers

What is the term used to describe the constant value by which each term in a geometric sequence is multiplied to obtain the next term?

<p>Common ratio (C)</p> Signup and view all the answers

What is the value of the common ratio 'r' in a geometric sequence if the second term is 6 and the first term is 3?

<p>$r = 2$ (C)</p> Signup and view all the answers

What is the sum of the first 5 terms of a geometric sequence if the first term is 2 and the common ratio is 3?

<p>$242$ (D)</p> Signup and view all the answers

Which of the following is NOT a condition for using the alternative formula for a finite geometric series?

<p>$r &lt; 1$ (C)</p> Signup and view all the answers

What is the value of 'a' in a geometric sequence if the sum of the first 4 terms is 15 and the common ratio is 2?

<p>$15/7$ (B)</p> Signup and view all the answers

What is the formula for the sum of a finite geometric series when the common ratio 'r' is less than 1?

<p>$a(1 - r^n) / (1 - r)$ (D)</p> Signup and view all the answers

What is the value of the sum of the first 3 terms of a geometric sequence if the first term is 2 and the common ratio is -2?

<p>$-14$ (D)</p> Signup and view all the answers

If the sum of the first n terms of a geometric sequence is 15 and the common ratio is 2, what can be said about the value of the first term?

<p>The first term cannot be determined. (B)</p> Signup and view all the answers

What happens to the value of S_n as n approaches infinity if |r| > 1?

<p>S_n grows without bound. (C)</p> Signup and view all the answers

If the sum of the first 5 terms of a geometric sequence is 242 and the common ratio is 3, what is the value of the first term?

<p>2/3 (B)</p> Signup and view all the answers

What is the relationship between the sum of the first n terms of a geometric sequence and the sum of the first (n - 1) terms?

<p>The sum of the first n terms is always equal to the sum of the first (n - 1) terms multiplied by the common ratio. (C)</p> Signup and view all the answers

If the sum of the first n terms of a geometric sequence is 15 and the sum of the first (n - 1) terms is 7.5, what is the value of the common ratio?

<p>3 (C)</p> Signup and view all the answers

What is the sum of the first n terms of a geometric sequence if the common ratio is -1 and the first term is 1?

<p>1 for all n (C)</p> Signup and view all the answers

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