7) 29/9; repeating
8) 301/20; terminating
9) -101/20; terminating
Answer:

Step-by-step explanation:
Let the x-axis be the time (in years) and the y-axis the value of the fax machine (in dollars).
We know that the initial value of the fax machine is $100; in other words, when the time is zero years, the value is $100, or as an ordered pair (0, 100). We also know that after 1 year the value decreases to $80, so (1, 80).
Now we can find the slope of the line passing through those two points using the slope formula

where
is the slope
are the coordinates of the first point
are the coordinates of the second point
Replacing values:


Now, to complete our model we are using the point slope formula

where
is the slope
are the coordinates of the first point
Replacing values:




We can conclude that the correct linear depreciation model is 
Answer: SECOND OPTION.
Step-by-step explanation:
It is important to remember that, by definition, the "Resultant vector " is the vector obtained by adding two or more vectors.
For this exercise you need to use the formula for calculate the magnitude of the resultant vector obtained by adding the vectors "a" and "b" shown in the picture attached:

Where "c" is the magnitude of the resultant vector asked in the exercise.
You need to analyze the graph given in the exercise.
You can identify that:

Then the next step, knowing which are "a" and "b", is to substitute values into the formula given at the beginning of this explanation, as following:

Finally, evaluating, you get that "c" is:
