SOLUTION: What is the value of c if the vertex of the parabola {{{y=x^2-8x+c}}} is a point one x-axis?

Question 468343: What is the value of c if the vertex of the parabola is a point one x-axis?
Answer by ccs2011(207) (Show Source): You can put this solution on YOUR website!
If the vertex is on the x_axis, then the y_value of vertex must be 0.
Vertex: (x_value, 0)
To determine x-value of vertex, use formula for finding line of symmetry

For the given parabola, a = 1, b = -8, c = c

Therefore the vertex is at (4,0)
To solve for c, plug in these values for x,y into given equation

So value of c is 16.
Any other value other than 16 would yield a vertex not on the x-axis.

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