Use the Formula for the General Term of a Geometric SequenceUse the formula for the general term (the nth term)of a geometric sequence to find the indicated term of the
sequence with the given first term, $$\mathbf { a } _ { 1 }$$ , and common ratio, r.
-$$5 , - 10,20 , - 40,80 , \ldots$$
A) $\mathrm { a } _ { \mathrm { n } } = 5 ( - 2 ) ^ { \mathrm { n } - 1 }$
B) $a _ { n } = 5 ( - 2 ) ^ { n }$
C) $a _ { n } = a _ { 1 } - 2 ^ { n }$
D) $a _ { n } = 5 ( - 2 n )$

Question

Quizplus · Accepted Answer

The given sequence is a geometric sequence with $$\mathbf { a } _ { 1 } = 5$$ and common ratio r = -2. 
Using the formula for the general term of a geometric sequence, we have:
$$a_n = a_1 * r^{n-1}$$
Substituting a1 and r into the formula, we get:
$$a_n = 5*(-2)^{n-1}$$
Therefore, the best choice is A.

Use the Formula for the General Term of a Geometric a1\mathbf { a } _ { 1 }a1​

Use the Formula for the General Term of a Geometric $\mathbf { a } _ { 1 }$