Find the vertex of this parabola
y=-x^2+8x-25

Dy/dx=-2x+8

dy/dx=0 when -2x+8=0, 2x=8, x=4

y(4)=-16+32-25=-9

So the vertex is (4,-9)

“exterior angles of triangles. an exterior (or external) angle is the angle between one side of a triangle and the extension of an adjacent side. try this drag the orange dots on any vertex to reshape the triangle.” look to get to the answer i explained what it means and other things i hope it you .

Ireally don’t understand your problem do you have a better picture of it