Really Need Help With Algebra 2 Word Problems?

Question

Ok, I will write the problem down belown, it is for a test and I am really confused

Hiring a backhoe and operator plus a variable cost that is a function of the hours worked. The total cost is given by the function c(x)= -3.75xsquared + 27x + 260, where c is the cost in dollars and x is the number of hours worked. For what value of x will this function be maximized?

please explain how i go about doing this!!

Answer 1

First: x must be greater than 0. You can't hire someone for negative time.
You could use the formula on the first link to find the roots of x, and look for the point halfway between. You could even use the second link to calculate the roots of x.

BUT- given y = ax^2+bx+c, all you NEED is to find -b/(2a).
Which is -27 / (-7.5) = 3.6