We know that the vertex form of any quadratic function is the form:
The given quadratic function is 
To convert it into the vertex form we will have to complete the square of the quadratic expression given here which may be done as shown below:
Thus, 
(This is because adding a 4 inside the parentheses to complete the square is equivalent to adding 16 to the whole expression and thus we need to subtract 16 from the overall expression.)
The above is the vertex form of the original given function, .
It would be: -0.375c - 11 = 13
-0.375c = 13 + 11
c = -24/0.375
c = -64
In short, Your Answer would be -64
Hope this helps!
Answer :
It would be -15 and -3
Option 1 : 20 + 1.25d
option 2 : 2.50d
when will they be equal......so set them equal to each other
20 + 1.25d = 2.50d
20 = 2.50d - 1.25d
20 = 1.25d
20 / 1.25 = d
16 = d.....so they will be equal at 16 dvd rentals
