Step-by-step explanation:
(g+f)(x) ie option B
-2+1 = -1
1-2 = -1
4-5 = - 1
Answer:

Step-by-step explanation:
As the given Augmented matrix is
![\left[\begin{array}{ccccc}9&-2&0&-4&:8\\0&7&-1&-1&:9\\8&12&-6&5&:-2\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bccccc%7D9%26-2%260%26-4%26%3A8%5C%5C0%267%26-1%26-1%26%3A9%5C%5C8%2612%26-6%265%26%3A-2%5Cend%7Barray%7D%5Cright%5D)
Step 1 :
↔
![\left[\begin{array}{ccccc}1&-14&6&-9&:10\\0&7&-1&-1&:9\\8&12&-6&5&:-2\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bccccc%7D1%26-14%266%26-9%26%3A10%5C%5C0%267%26-1%26-1%26%3A9%5C%5C8%2612%26-6%265%26%3A-2%5Cend%7Barray%7D%5Cright%5D)
Step 2 :
↔
![\left[\begin{array}{ccccc}1&-14&6&-9&:10\\0&7&-1&-1&:9\\0&124&-54&77&:-82\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bccccc%7D1%26-14%266%26-9%26%3A10%5C%5C0%267%26-1%26-1%26%3A9%5C%5C0%26124%26-54%2677%26%3A-82%5Cend%7Barray%7D%5Cright%5D)
Step 3 :
↔
![\left[\begin{array}{ccccc}1&-14&6&-9&:10\\0&1&-\frac{1}{7} &-\frac{1}{7} &:\frac{9}{7} \\0&124&-54&77&:-82\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bccccc%7D1%26-14%266%26-9%26%3A10%5C%5C0%261%26-%5Cfrac%7B1%7D%7B7%7D%20%26-%5Cfrac%7B1%7D%7B7%7D%20%26%3A%5Cfrac%7B9%7D%7B7%7D%20%5C%5C0%26124%26-54%2677%26%3A-82%5Cend%7Barray%7D%5Cright%5D)
Step 4 :
↔
,
↔
![\left[\begin{array}{ccccc}1&0&4&-11&:-8\\0&1&-\frac{1}{7} &-\frac{1}{7} &:\frac{9}{7} \\0&0&- \frac{254}{7} &\frac{663}{7} &:-\frac{1690}{7} \end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bccccc%7D1%260%264%26-11%26%3A-8%5C%5C0%261%26-%5Cfrac%7B1%7D%7B7%7D%20%26-%5Cfrac%7B1%7D%7B7%7D%20%26%3A%5Cfrac%7B9%7D%7B7%7D%20%5C%5C0%260%26-%20%5Cfrac%7B254%7D%7B7%7D%20%26%5Cfrac%7B663%7D%7B7%7D%20%26%3A-%5Cfrac%7B1690%7D%7B7%7D%20%5Cend%7Barray%7D%5Cright%5D)
Step 5 :
↔
![\left[\begin{array}{ccccc}1&0&4&-11&:-8\\0&1&-\frac{1}{7} &-\frac{1}{7} &:\frac{9}{7} \\0&0&1&-\frac{663}{254} &:-\frac{1690}{254} \end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bccccc%7D1%260%264%26-11%26%3A-8%5C%5C0%261%26-%5Cfrac%7B1%7D%7B7%7D%20%26-%5Cfrac%7B1%7D%7B7%7D%20%26%3A%5Cfrac%7B9%7D%7B7%7D%20%5C%5C0%260%261%26-%5Cfrac%7B663%7D%7B254%7D%20%26%3A-%5Cfrac%7B1690%7D%7B254%7D%20%5Cend%7Barray%7D%5Cright%5D)
Step 6 :
↔
,
↔
![\left[\begin{array}{ccccc}1&0&0&-\frac{71}{127} &:\frac{176}{127} \\0&1&0&-\frac{131}{254} &:\frac{284}{127} \\0&0&1&-\frac{663}{254} &:\frac{845}{127} \end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bccccc%7D1%260%260%26-%5Cfrac%7B71%7D%7B127%7D%20%26%3A%5Cfrac%7B176%7D%7B127%7D%20%5C%5C0%261%260%26-%5Cfrac%7B131%7D%7B254%7D%20%26%3A%5Cfrac%7B284%7D%7B127%7D%20%5C%5C0%260%261%26-%5Cfrac%7B663%7D%7B254%7D%20%26%3A%5Cfrac%7B845%7D%7B127%7D%20%5Cend%7Barray%7D%5Cright%5D)
∴ we get

i know the answer to be "B" because we just learned this in class
That's geometric sequence
T7 = T5*r^2 = T5+1920
r = 2, so
4*T5 = T5 + 1920
3T5 = 1920
T5 = 640
640 = 2^4 * 40
So, a=40 and the sequence is
40 80 160 320 640 1280 2560 5120 10240 20480 40960 ...
Note that 2560 = 640 + 1920
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