Q:

How can you find the equation of a parabola?

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Quick Answer

To find the equation of a parabola, substitute the vertex coordinates for h and k, substitute the coordinates of another point on the parabola for x and y and then solve for a. The equations will differ depending on whether the parabola is vertical or horizontal.

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Full Answer

The equation for a vertical parabola is y=a(x-h)2+k and the equation for a horizontal is x=a(y-k)2+h. The steps to solve the equation remain the same.

Step 1: Use the right formula and plug in the numbers

Determine whether the parabola is vertical or horizontal. Substitute the coordinates for the vertex into h and k in the formula. Choose a point on the figure, other than the vertex, and substitute those coordinates into x and y in the formula.

Step 2: Solve for the value of a

Once all of the numbers have been plugged in, use simple algebra to solve for the value of a in the formula.

Step 3: Rewrite the formula

Rewrite the formula using the vertex coordinates for the values of h and k, and the value for a that was obtained from the calculation in Step 2. The final answer will resemble an algebra problem, with unknowns represented by x and y. An example of an equation for a vertical parabola is y=2(x-5)2+3.

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