Answer :
The equation of a parabola in vertex form is given by
[tex]f(x)=a(x-h)^2\text{ + k}[/tex]The vertex (h,k) when compared with the equation, h = 5 and k = -4
Since the concavity is -3,
a= -3
[tex]y=-3(x-5)^2\text{ + (-4)}[/tex][tex]\begin{gathered} y=-3(x-5)^2\text{ -4} \\ y=-3(x^2-10x+25\text{) - 4} \\ y=-3x^2\text{ + 30x -75 -4} \\ y=-3x^2\text{ + 30x -79} \end{gathered}[/tex]From the graph shown, it can be seen that the parabolic curve is concave down
To get the y-intercept
we will have to put x = 0 into the equation
[tex]\begin{gathered} y\text{ = -3(0) + 30 (0) - 79} \\ y-intercept\text{ = -79} \end{gathered}[/tex]