If 840 CLASS eighth graders, making up 4/5 of total eighth, studied algebra during summer, how many eighth graders are enrolled
1 answer:
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Answer:
- y = -2(x -3)² +24
- 16 feet
Step-by-step explanation:
We expect the equation for y to be quadratic. Since the table is obviously symmetrical about x=3, we can start with the vertex form ...
y = a(x -3)² +b
Filling in the values from the first two table points, we get
For (x, y) = (0, 6):
6 = a(0 -3)² + b ⇒ 9a +b = 6
For (x, y) = (2, 22):
22 = a(2-3)² +b ⇒ a +b = 22
Subtracting the second equation from the first gives ...
(9a +b) -(a +b) = (6) -(22)
8a = -16 . . . . . . collect terms
a = -2 . . . . . . . . divide by 8
The second equation above tells us ...
b = 22 -a = 22 -(-2) = 24
So, our equation for y is ...
y = -2(x -3)² +24
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The value of y for x=5 is ...
y = -2(5 -3)² +24 = 16
The height of the ball after 5 seconds is 16 feet.
