Answer:
Credit remaining after 21 minutes = $30.4
Step-by-step explanation:
Credit remaining on a phone card is a linear function of the total calling time.
When graphed, let the linear function representing the line is,
y = mx + b
Where 'm' = slope of the line
b = y-intercept
From the graph,
Slope of the line = -0.12
y = -0.12x + b
If this line passes through a point (33, 28.96),
28.96 = -0.12(33) + b
b = 28.96 + 3.96
b = 32.92
Therefore, the linear function is,
f(x) = -0.12x + 32.92
where x = calling time
Credit left in the card after 21 minutes,
f(21) = -0.12(21) + 32.92
= -2.52 + 32.92
= $30.4
Answer: B
Step-by-step explanation: if you divide 27/30 by 3 you get 9/10
Answer: 120 ft
<u>Step-by-step explanation:</u>
The Ellipse equation is:
where
- (h, k) is the center
- "a" is the horizontal radius
- "b" is the vertical radius
- c is the distance from the center to the foci: |a² - b²| = c²
Given: horizontal diameter = 122 → horizontal radius = 61 = a
vertical diameter = 22 → vertical radius = 11 = b
Foci (c): 61² - 11² = c²
3721 - 121 = c²
3600 = c²
±60 = c
Let (h, k) = (0, 0)
Then the foci are located at -60 and +60.
The distance between them is 60 + 60 = 120
The quadratic function in vertex form is:
y = a(x - h)^2 + k
Where:
vertex = (h, k)
Axis of symmetry: x = h
The value of “a” determines whether the graph opens up or down, and makes the parent function wider or narrower.
The value of “h” determines how far left or right the parent function is translated.
The value of “k” determines how far up or down the parent function is translated.
Now that we have these definitions, we can substitute the given values into the vertex form to solve for “a”:
Use vertex = (-4, -1) and y-intercept, (0, 7):
7 = a(0+ 4)^2 - 1
7 = a(4)^2 - 1
7 = a(16) - 1
Add 1 to both sides:
7 + 1 = a(16) - 1 + 1
8 = 16a
Divide both sides by 16 to solve for “a”:
8/16 = 16a/16
1/2 = a
Since a = 1/2 (which is positive, implying that the parabola opens upward), and the vertex occurs at point (-4, -1) as the minimum point:
The quadratic equation in vertex form is:
y = 1/2(x + 4)^2 - 1
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