Question 501396
find the vertex, line of symmetry, minimum or maximum value of the quadratic function and graph the function f(x)=-x^2+10x+3
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f(x)=-x^2+10x+3
complete the square
y=-(x^2-10x+25)+3+25
y=-(x-5)^2+28
This is an equation for a parabola of standard form: y=A(x-h)^2+k, (h,k) being the (x,y) coordinates of the vertex.
For given function, y=-(x-5)^2+28:
vertex: (5, 28)
negative sign for lead coefficient means parabola opens downward, has a maximum of 28
axis of symmetry: x=5
see graph below as a visual check on answers:

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{{{ graph( 300, 300, -10, 10, -10, 30,-x^2+10x+3) }}}