When in doubt, draw a picture. The vertex of the equation is at (3,0) and the y-intercept is at (0,4.5). The answer is D
You could either divide the 6 on each side and have 4=-3+x, so x=7, or you could distribute the 6 into the expression, so 24=-18+6x. Then 42=6x, and x=7.
The purpose of the quadratic formula is to easily obtain the x-coordinate of the vertex's location. The goal is to solve the equation by isolating x on one side of the equation, just like you would any other equation.
In step 7, take the square root of both sides. Note that you must account for the negative side of the square root, so add the +/- to the right side (not necessary for the left side because you want the x to be positive when you are finished, and you still get the same answer even if you assume the left side is negative).
Next, subtract b/2a from both sides and simplify the denominator of the root to be 2a.
Finally combine the terms to have a single denominator.
<span>Sales went from 48 pairs to 60 pairs:
total change = 60 - 48 = 12
percentage change = 12 / 48 = 0.25 = 0.25*100% = 25%
Answer: 25%</span>