SOLUTION: what is the equation of the line of symmetry for y = -x² + 4x + 5

what is the equation of the line of symmetry for y = -x² + 4x + 5

The vertex for the quadratic equation:

y = ax² + bx + c

is given by the formula:

(, ), where D = discriminant = 

and the line of symmetry is the vertical line
whose equation is 

x = 

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For the quadratic equation:

y = -x² + 4x + 5

a = -1, b = 4, c = 5

D = discriminant =  =  =  = 

So the vertex is

(, ) = (, ) = 
(, ) = (, ),    

and the line of symmetry is the vertical line
whose equation is 

x = 

or

x = 2

Here is the graph of the quadratic and the
green vertical line is the line of symmetry,
notice it crosses the x axis at 2.



Edwin