3. two car washes charge a basic fee plus a fee based on the number of extras that
are chosen. the table below shows the total costs for different car washes at
bubbles car wash. the total cost y (in dollars) for a car wash with x extras at
soapy car wash is represented by the equation y = x + 9. which car wash
charges more for the basic fee? how many extras must be chosen for the total
costs to be the same?
number of extras, x2
total cost, y
9
12
15
18

let's cover over the formula of the vertex:

y = a(x – h)^2 + k

in this formula, (h,k) are the vertex, always remember that the positive or negative value of the vertex is based on the sign it has.

for example, if the vertex is -3,-6 then both the x and y value would have the positive sign attached to it and if it were a positive x and y value, then a negative sign would be attached to it.

with that being said, for our problem the x value is a positive one so we are looking for a number with a negative sign next to it, in this case the first and second choice.

however, for the first answer choice it isn't quite part of the formula so we know that the answer choice correctly displays the x value.

to confirm, we can see if the -1 fits correctly with the second answer choice, and as mentioned above a negative number will have a positive sign attached to it. so, for our problem we can see that -1 has been changed to +1, so we can confirm that the second answer choice is correct.

hence, our final answer is y=(x - 1)^2 + 1

3+x

step-by-step explanation: