I got 20 as my answer but don’t use this answers they’re is more answers coming
Check the picture below.
so, we know the parabola has a vertex at (0 , 50), we also know it passes through (60 , 0), so then
![~~~~~~\textit{vertical parabola vertex form} \\\\ y=a(x- h)^2+ k\qquad \begin{cases} \stackrel{vertex}{(h,k)}\\\\ \stackrel{"a"~is~negative}{op ens~\cap}\qquad \stackrel{"a"~is~positive}{op ens~\cup} \end{cases} \\\\[-0.35em] \rule{34em}{0.25pt}](https://tex.z-dn.net/?f=~~~~~~%5Ctextit%7Bvertical%20parabola%20vertex%20form%7D%20%5C%5C%5C%5C%20y%3Da%28x-%20h%29%5E2%2B%20k%5Cqquad%20%5Cbegin%7Bcases%7D%20%5Cstackrel%7Bvertex%7D%7B%28h%2Ck%29%7D%5C%5C%5C%5C%20%5Cstackrel%7B%22a%22~is~negative%7D%7Bop%20ens~%5Ccap%7D%5Cqquad%20%5Cstackrel%7B%22a%22~is~positive%7D%7Bop%20ens~%5Ccup%7D%20%5Cend%7Bcases%7D%20%5C%5C%5C%5C%5B-0.35em%5D%20%5Crule%7B34em%7D%7B0.25pt%7D)
![\stackrel{vertex}{(0~~,~~50)}\implies y=a(x-0)^2+50\implies y = ax^2+50 \\\\\\ \begin{cases} x =60\\ y = 0 \end{cases}\implies 0=a6^2+50\implies -50=3600a\implies -\cfrac{50}{3600}=a \\\\\\ -\cfrac{1}{72}=a~\hfill therefore~\hfill \boxed{y=-\cfrac{1}{72}x^2+50}](https://tex.z-dn.net/?f=%5Cstackrel%7Bvertex%7D%7B%280~~%2C~~50%29%7D%5Cimplies%20y%3Da%28x-0%29%5E2%2B50%5Cimplies%20y%20%3D%20ax%5E2%2B50%20%5C%5C%5C%5C%5C%5C%20%5Cbegin%7Bcases%7D%20x%20%3D60%5C%5C%20y%20%3D%200%20%5Cend%7Bcases%7D%5Cimplies%200%3Da6%5E2%2B50%5Cimplies%20-50%3D3600a%5Cimplies%20-%5Ccfrac%7B50%7D%7B3600%7D%3Da%20%5C%5C%5C%5C%5C%5C%20-%5Ccfrac%7B1%7D%7B72%7D%3Da~%5Chfill%20therefore~%5Chfill%20%5Cboxed%7By%3D-%5Ccfrac%7B1%7D%7B72%7Dx%5E2%2B50%7D)
so then, what's "y" when x = 25?
![y=-\cfrac{1}{72}25^2+50\implies y = -\cfrac{625}{72}+50\implies y = \cfrac{2975}{72}\implies y\approx 41.32](https://tex.z-dn.net/?f=y%3D-%5Ccfrac%7B1%7D%7B72%7D25%5E2%2B50%5Cimplies%20y%20%3D%20-%5Ccfrac%7B625%7D%7B72%7D%2B50%5Cimplies%20y%20%3D%20%5Ccfrac%7B2975%7D%7B72%7D%5Cimplies%20y%5Capprox%2041.32)
It’s A you just multiply the keys
A to Predict planetary changes