12 decreased by 8 times a number is 36
1 answer:
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Answer:
D(x) is a function
D(x) is a direct variation
D(x) is a rule for the set of points (5.10). (6, 12) and (-2,-4)
Step-by-step explanation:
we know that
A relationship between two variables, x, and y, represent a proportional variation if it can be expressed in the form or
In a proportional relationship the constant of proportionality k is equal to the slope m of the line and the line passes through the origin
In this problem
D(x) is a direct variation (linear function)
The variable x is the independent variable or input value
The variable D(x) is the dependent variable or output value
<u><em>Verify each statement</em></u>
case 1) D(x) is a function
The statement is true
see the explanation
case 2) x is the dependent variable
The statement is false
The variable x is the independent variable or input value
case 3) D(x) is a direct variation
The statement is true
see the explanation
case 4) D(x) is a rule for the set of points (5.10). (6, 12) and (-2,-4)
The statement is true
Because
For x=5
substitute in the linear equation
---> is ok
For x=6
substitute in the linear equation
---> is ok
For x=-2
substitute in the linear equation
---> is ok
Refer to the diagram shown below.
The directrix is y = -4 and the focus is (-2, -2).
Therefore the vertex is at (-2, -3).
Consider an arbitrary point (x,y) on the parabola.
The square of distance from the focus to the point is
(x+2)² + (y+2)²
The square of the distance from the point to the directrix is
(y+4)²
Therefore
(y+4)² = (y+2)² + (x+2)²
y² + 8y + 16 = y² + 4y + 4 + (x+2)²
4y = (x+2)² - 12
y = (1/4)(x+2)² - 3
Answer:
The directrix is y = -4 and the focus is (-2, -2).
Therefore the vertex is at (-2, -3).
Consider an arbitrary point (x,y) on the parabola.
The square of distance from the focus to the point is
(x+2)² + (y+2)²
The square of the distance from the point to the directrix is
(y+4)²
Therefore
(y+4)² = (y+2)² + (x+2)²
y² + 8y + 16 = y² + 4y + 4 + (x+2)²
4y = (x+2)² - 12
y = (1/4)(x+2)² - 3
Answer: