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Algebra Examples
Step 1
Subtract from both sides of the equation.
Step 2
Use the vertex form, , to determine the values of , , and .
Step 3
Find the vertex .
Step 4
Step 4.1
Find the distance from the vertex to a focus of the parabola by using the following formula.
Step 4.2
Substitute the value of into the formula.
Step 4.3
Cancel the common factor of .
Step 4.3.1
Cancel the common factor.
Step 4.3.2
Rewrite the expression.
Step 5
Step 5.1
The directrix of a parabola is the horizontal line found by subtracting from the y-coordinate of the vertex if the parabola opens up or down.
Step 5.2
Substitute the known values of and into the formula and simplify.
Step 6