So we can write is also as:
k=2y+x
y=(k-x)/2
x=k-2y
k= 2[(k-x)/2] + (k-2y)
Answer:
<em>a7=-1</em>
Step-by-step explanation:
<em>Arithmetic Sequences</em>
The arithmetic sequences can be identified because each term n is obtained by adding or subtracting a fixed number to the previous term n-1.
The equation to calculate the nth term of an arithmetic sequence is:
![a_n=a_1+(n-1)r](https://tex.z-dn.net/?f=a_n%3Da_1%2B%28n-1%29r)
We know: a12=29, a16=53, now we use the above equation for n=12 and n=16:
![a_1+(12-1)r=29](https://tex.z-dn.net/?f=a_1%2B%2812-1%29r%3D29)
![a_1+(16-1)r=53](https://tex.z-dn.net/?f=a_1%2B%2816-1%29r%3D53)
Simplifying both equations:
![a_1+11r=29](https://tex.z-dn.net/?f=a_1%2B11r%3D29)
![a_1+15r=53](https://tex.z-dn.net/?f=a_1%2B15r%3D53)
Subtracting:
![4r=53-29=24](https://tex.z-dn.net/?f=4r%3D53-29%3D24)
Solving:
r=24/4
r=6
The 7th term can be found as 9 terms before the 16th:
![a_7=a_{16}-9r](https://tex.z-dn.net/?f=a_7%3Da_%7B16%7D-9r)
![a_7=53-9*6=53-54=-1](https://tex.z-dn.net/?f=a_7%3D53-9%2A6%3D53-54%3D-1)
Thus: a7=-1
<span>19 + 57 + 9 = 85
Do you need farther explaining</span>
Answer:
Step-by-step explanation:
Ok