4. what is the rule of the nth term of the geometric sequence with = -18 and the common ratio r = 2? a. b. c. d. e.

Step-by-step explanation:

The common ratio is given as 2, so the base of any exponential must be 2 (not -2 or 2.25). The 4th term is negative, so the initial value must be negative (since the multiplying factor is positive). The only selection matching these requirements is d.

You know the general term is ...

... an = a1·r^(n-1)

so the 4th term is

... -18 = a1·2^(4-1) = 8·a1

Then the first term is ...

... a1 = -18/8 = -2.25 . . . . . confirms our choice of answer d.

d. bc = 12 and ef = 16

step-by-step explanation:

we are given that δabc : δdef such that .

also, it is given that

so, from the options, we need that .

a.

b.

c.  

d.

as, we can see that only option d gives the same ratio as i.e. .

hence, the possible lengths are bc = 12 and ef = 16.