Question

Independent Practice

Write an explicit rule for a geometric sequence that has 1 as its first term and a common ratio of –4. What is the seventh term of this sequence?


A.
an=−4 · (1)n−1; −4a subscript n baseline equals negative 4 times left parenthesis 1 right parenthesis superscript n minus 1 baseline semi-colon negative 4


B.
an=−4 · (7)n−1; −470,596a subscript n baseline equals negative 4 times left parenthesis 7 right parenthesis superscript n minus 1 baseline semi-colon negative 470,596


C.
an=1 · (−4)n−1; 4,096a subscript n baseline equals 1 times left parenthesis negative 4 right parenthesis superscript n minus 1 baseline semi-colon 4,096


D.
an=1 · (−4)n; −16,384a subscript n baseline equals 1 times left parenthesis negative 4 right parenthesis superscript n baseline semi-colon negative 16,384

Answer 1

Answer: The Answer Is Letter B Or Letter C..... 12*4*2= 96

B.

an=−4 · (7)n−1; −470,596a subscript n baseline equals negative 4 times left parenthesis 7 right parenthesis superscript n minus 1 baseline semi-colon negative 470,596

C.

an=1 · (−4)n−1; 4,096a subscript n baseline equals 1 times left parenthesis negative 4 right parenthesis superscript n minus 1 baseline semi-colon 4,096

Step-by-step explanation: First Term: 2, Second Term: 6, Third Term: 18, Forth Term: 54, Fifth Term: 162

Geometric sequences and series

A geometric sequence is a sequence of numbers that follows a pattern were the next term is found by multiplying by a constant called the common ratio, r.

Example

Write the first five terms of a geometric sequence in which a1=2 and r=3.

We use the first given formula:

Just as with arithmetic series it is possible to find the sum of a geometric series. It is found by using one of the following formulas:

Video lesson

Use the formula for the sum of a geometric series to determine the sum when a1=4 and r=2 and we have 12 terms.