I’m year 11 and doing a old Maths paper at the moment and I’ve come to the exellence question.

I have a parabola that has the following co ordinates and i am in desperate need on how to make them in to a quadratic equation

(5, 0)

(25,0)

(15,10) thats the maximum

there’s no Y intersept as the graph doessn’t show it

the answer sheet gives the equation:

y = -0.1(x-15)^2+10

any help on how they got that would be much appreciated