You've got a formula. If the two endpoints are

and

, then the length is

. The result is

.
Answer:
y = 5x + 4
Step-by-step explanation:
First I found the slope by using the the definition that slope is rise/run so I saw that the y value went up from 4 to 9 which is 5 units and then the x value went up one in that same time. This means that the slope is 5/1. Then I found the y intercept by seeing where x = 0. On the graph you can see the line touches the y - axis at a value of 4 which means that the y - intercept is 4. Plugging these values into the y = mx + b equation you get y = 5x + 4.
y = mx + b, where m = slope, and b = y-intercept.
Since you are not given the y-intercept, you have to solve for it through the equation, y = (4/5)x (which is the slope you are given) + b, and replace x and y with values given, which are (-5,-3)
y = (4/5)x + b
-3 = (4/5)(-5) + b
-3 = -4 + b
1 = b
Then replace b in the first equation to get the answer
y = (4/5)x + 1
Answer:

Used a calculator to find all the square roots, .06's is 0.24, which is the closest out of all of the options to the graph.