Question

Write an equation (any form) for the quadratic graphed below:
I added the photo of the graph

Answer 1

Check the picture below.

so we are really looking for the equation of a parabola whose vertex is at (2 , 3) and it passes through (4 , 1)

`~~~~~~\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] ~\dotfill\\\\ \begin{cases} h=2\\ k=3\\ \end{cases}\implies y=a(~~x-2~~)^2 + 3\hspace{4em}\textit{we also know that} \begin{cases} x=4\\ y=1 \end{cases}`

`1=a(4-2)^2+3\implies -2=a(2)^2\implies -2=4a \\\\\\ \cfrac{-2}{4}=a\implies -\cfrac{1}{2}=a~\hfill \boxed{y=-\cfrac{1}{2}(x-2)^2 + 3}`