SOLUTION: The graph of y=ax^2 -4x + c had x-intercepts of -1 and 5. Find the values of a and c. Find the minimum value of y.

Question 1151642: The graph of y=ax^2 -4x + c had x-intercepts of -1 and 5. Find the values of a and c. Find the minimum value of y.
Answer by rothauserc(4718) (Show Source): You can put this solution on YOUR website!
(x+1) * (x-5) = 0
:
x^2 -4x -5 = 0
:
a = 1, c = -5
:
The graph of this equation is a parabola that curves upward, therefore the minimum value of y is the y-coordinate of the parabola's vertex
:
x-coordinate of the vertex = -b/2a = -(-4)/2(1) = 4/2 = 2
:
substitute for x in the parabola's equation
:
y-coordinate = 2^2 -4(2) -5 = -9
:
The minimum value for y is -9
:
Here is the graph of the parabola
:

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