Something funny is that the x value of the vertex lies directl in the middle of the x intercepts
so
we see the x intercepts or 0's at x=8 and 2
the average is x=5
so find f(5) to find the y value of the vertex
f(5)=(5-8)(5-2)
f(5)=(-3)(3)
f(5)=-9
vertex is at (5,-9)
the actual way the teacher wants is to expand then compltete the square to get into the form f(x)=a(x-h)^2+k where the vertex is (h,k)
but whatever
verrtex is at (5,-9)
a easy way to remember how to divide is KCF Keep the first fraction Change the division to multiplication and Flip the second fraction. 1/2*8/1 =8/2 =4
Increase = 15.96 - 13.30
Increase = 2.66
percentage of the increase = 2.66/13.30 x 100 = 20%
Your answer will be 45. Hope this helps!