You add each number by 6n - fourth choice. I am not sure if this is the right answer.
The vertex form:
![y=a(x-h)^2+k](https://tex.z-dn.net/?f=y%3Da%28x-h%29%5E2%2Bk)
(h,k) - the coordinates of the vertex
![y-13=2(x+4)^2 \\ y=2(x+4)^2+13 \\ y=2(x-(-4))^2+13 \\ \\ h=-4 \\ k=13](https://tex.z-dn.net/?f=y-13%3D2%28x%2B4%29%5E2%20%5C%5C%0Ay%3D2%28x%2B4%29%5E2%2B13%20%5C%5C%0Ay%3D2%28x-%28-4%29%29%5E2%2B13%20%5C%5C%20%5C%5C%0Ah%3D-4%20%5C%5C%20k%3D13)
The coordinates of the vertex are
(-4,13).
It would be 96 because V=(9)(32)= 288/3=96
21/7 = 3 so then, 105/7 = x which is 15
The mean of n numbers is the sum of the numbers divided by n.
You have a mean score of 84 after taking 5 tests. Let x be the sum of scores.
![\frac{x}{5}=84 \\ x=84 \times 5 \\ x=420](https://tex.z-dn.net/?f=%5Cfrac%7Bx%7D%7B5%7D%3D84%20%5C%5C%0Ax%3D84%20%5Ctimes%205%20%5C%5C%0Ax%3D420)
You scored a total of 420 points on five tests.
You need to have a mean score of 85 after taking 6 tests. Let y be the score you need to obtain. Your total score on 6 tests is 420+y.
![\frac{420+y}{6}=85 \\ 420+y=85 \times 6 \\ 420+y=510 \\ y=510-420 \\ y=90](https://tex.z-dn.net/?f=%5Cfrac%7B420%2By%7D%7B6%7D%3D85%20%5C%5C%0A420%2By%3D85%20%5Ctimes%206%20%5C%5C%0A420%2By%3D510%20%5C%5C%0Ay%3D510-420%20%5C%5C%0Ay%3D90)
You need to score 90 points on the sixth test.