the answer is 34.83 I believe 
 
        
             
        
        
        
Answer:
When we have a quadratic equation:
a*x^2 + b*x + c = 0
There is something called the determinant, and this is:
D = b^2 - 4*a*c
If D < 0, then the we will have complex solutions.
In our case, we have
5*x^2 - 10*x + c = 0
Then the determinant is:
D = (-10)^2 - 4*5*c = 100 - 4*5*c
And we want this to be smaller than zero, then let's find the value of c such that the determinant is exactly zero:
D = 0 = 100 - 4*5*c
     4*5*c = 100  
        20*c = 100
             c = 100/20 = 5
As c is multiplicating the negative term in the equation, if c increases, then we will have that D < 0.
This means that c must be larger than 5 if we want to have complex solutions,
c > 5.
I can not represent this in your number line, but this would be represented with a white dot in the five, that extends infinitely to the right, something like the image below:
 
        
             
        
        
        
Step-by-step explanation:
 4 is the A or Ampltiude
To find the period set it equal to 2 pi/B


b=

b=

There is no phase shift
 The midline or d or vertical shift  is 1.
Our equation for 8 is 

9.Use sin function. The a value is 2 or -2 your choice.
Set up the period equal to the equation



Which equal 6. 
B=6
There is no C and the D and Vertical Shift is 1.
Our equation is 

 
        
             
        
        
        
Answer:  F) 7 mph
<u>Step-by-step explanation:</u>
The line you drew is correct but you read the graph wrong.  
The line drawn from 15 hours of training (bottom axis) meets the "line of best fit" at the average running speed (left axis) between 6 and 8, which is 7.