Algebra 2 Need help with b

Answer:
a. was incorrect a = -0.109569028 so...
y = -0.109569028(x + 7)² + 54
b. It's been the above vertex equation for a parabola then
set y = 40 equal to the parabolic equation, we get
40 = -0.109569028x² - 1.533966392x + 48.631117628
solve for x we get
x = -18.3036867393939 or ~ 18.3 feet
Step-by-step explanation:
y = a(x - h)² + k
(h, k) = vertex = (-7, 54)
x = h is the axis of symmetry -7
y = a(x -(-7))² + 54
y = a(x + 7)² + 54
solve for a by inputting the point (15.2, 0)
0 = a(15.2 + 7)² + 54
-54 = a(22.2)²
-54 = 492.84a
a = -54/492.84
a = -0.109569028