SOLUTION: the parabola's directrix is parallel to the x-axis, and the parabola passes through points at (1,1) (0,9) and (2,1). Write the equation of the parabola.

Question 730844: the parabola's directrix is parallel to the x-axis, and the parabola passes through points at (1,1) (0,9) and (2,1).
Write the equation of the parabola.
Answer by josgarithmetic(39620) (Show Source): You can put this solution on YOUR website!
The points given will suggest that the vertex is for x=3/2. This is because of parabola having left-right symmetry. (1, 1) and (2, 1) are equally spaced about the axis of symmetry. The standard form equation will be something like y=a(x-3/2)^2+k. This equation has two unknowns and you will use two of the given points to make a system of two equations and two unknown variables, and then solve the system for those variables.

Form the system from these three:

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