I approached this one a little differently from Melody, but I think we end up with the same solution.
Like her, since x= 2 and x=7 are "zeroes," the x coordinate (because of symmetry) must be at x = 4.5.
And the vertex is given by (4.5, 25)...so.....in "vertex" form, we have...
y = a(x - 4.5)^2 + 25 and we need to find "a"
And we know that when x = 7, y = 0....so we have
0 = a(7 - 4.5)^2 + 25 subtract 25 from both sides
-25 = a(6.25) divide both sides by 6.25
a = -4 and this should be correct, since the parabola turns "downward"
So, our function is
y = -4(x - 4.5)^2 + 25
Here's the graph.......https://www.desmos.com/calculator/ewlw8wwdni
Yep...that seems correct.....