an example that opposes or contradicts an idea or theory.
The third graph represents a function.
In a function, every input (x value) has <em>exactly</em> one output (y value). If even a single input has zero or two outputs, the graph does not represent a function.
A good way of testing this is using a vertical line. As you move a vertical line from left to right across a graph, it should always be touching exactly one point on the graphed line.
In this case, every graph fails this vertical line test except for the third graph, so the third graph represents a function.
If you input: 1/0.00000001 in a calculator, the result will be a very large number
so as you get closer to zero, the result of 1/x larger until it becomes infinite (or undefined as some people like to call it) at 1/0
The guy ran at a speed of 8.07783 MPH
Here's how I got my answer:
1 km/hr. = 0.621371
So, if you do 
you will get your answer: 8.07783 MPH
there are many combinations for it, but we can settle for say
![\bf \begin{cases} f(x)=x+2\\[1em] g(x)=\cfrac{9}{x^2}\\[-0.5em] \hrulefill\\ (f\circ g)(x)\implies f(~~g(x)~~) \end{cases}\qquad \qquad f(~~g(x)~~)=[g(x)]+2 \\\\\\ f(~~g(x)~~)=\left[ \cfrac{9}{x^2} \right]+2\implies f(~~g(x)~~)=\cfrac{9}{x^2}+2](https://tex.z-dn.net/?f=%5Cbf%20%5Cbegin%7Bcases%7D%20f%28x%29%3Dx%2B2%5C%5C%5B1em%5D%20g%28x%29%3D%5Ccfrac%7B9%7D%7Bx%5E2%7D%5C%5C%5B-0.5em%5D%20%5Chrulefill%5C%5C%20%28f%5Ccirc%20g%29%28x%29%5Cimplies%20f%28~~g%28x%29~~%29%20%5Cend%7Bcases%7D%5Cqquad%20%5Cqquad%20f%28~~g%28x%29~~%29%3D%5Bg%28x%29%5D%2B2%20%5C%5C%5C%5C%5C%5C%20f%28~~g%28x%29~~%29%3D%5Cleft%5B%20%5Ccfrac%7B9%7D%7Bx%5E2%7D%20%5Cright%5D%2B2%5Cimplies%20f%28~~g%28x%29~~%29%3D%5Ccfrac%7B9%7D%7Bx%5E2%7D%2B2)
