Engage with knowledgeable experts and get accurate answers on IDNLearn.com. Discover prompt and accurate answers from our experts, ensuring you get the information you need quickly.

find g12 in the sequence -1,-3,-9,-27,....
a. -59,049
b. -177,147
c. 118,098
d. -19,683


Sagot :

Answer:

b. [tex]a_{12}=-177147[/tex]

Step-by-step explanation:

This is a geometric sequence:

[tex]a_n=a_1x^{n-1}[/tex]

where n is the index in the sequence and x is the common scale factor.

In the given sequence here, the common factor is 3:

[tex]-3\div-1=3\\-9\div-3=3\\-27\div-9=3[/tex]

That's the factor, and we know the first term is -1, so you can write the equation for this sequence:

[tex]a_n=(-1)(3)^{n-1}[/tex]

Finally, plug in 12 for n and solve:

[tex]a_{12}=(-1)(3)^{12-1}\\a_{12}=(-1)(3)^{11}\\a_{12}=(-1)177147\\a_{12}=-177147[/tex]