Answer:
see attached
Step-by-step explanation:
It's almost easier for you to do this than it is to post a question on Brainly.
All you need to do is type the relevant expressions. Once you have Desmos show you the vertex, writing the x= equation for that is all that is required to draw it.
Answer:

Step-by-step explanation:
For this case in order to select the one admiral, captain and commander, all different. We are assuming that the order in the selection no matter, so we can begin selecting an admiral then a captain and then a commander.
So we have 10C1 ways to select one admiral since we want just one
Now we have remaining 9 people and we have 9C1 ways to select a captain since we want a captain different from the admiral selected first
Now we have remaining 8 people and we have 8C1 ways to select a commander since we want a commander different from the captain selected secondly.
The term nCx (combinatory) is defined as:

And by properties 
So then the number of possible way are:

If we select first the captain then the commander and finally the admiral we have tha same way of select 
For all the possible selection orders always we will see that we have 720 to select.
N-1(-1/2) is the formula because the sequence is taking half of the previous number and changing its sign
All I can say is that your equation is wrong