QUESTION IMAGE
Question
match the equation with the focus, vertex, directrix, and axis of symmetry. use the blank graph on the next question if you want to sketch the graph to help you determine the attributes.
| equation | vertex | focus | axis of symmetry | directrix |
|---|
(-4, -1) (5, 3) (0, 4) (3, 5) (1, 3) (-1, -4) (-2, -1) (-1, -3) y = -1
x = 0 y = 0 x = -3 x = -1 y = 3 y = -3
Step1: Recall formula for parabola
The equation of a parabola of the form $x = a(y - k)^2+h$ has vertex $(h,k)$. Here $h=-2,k = - 1,a=-\frac{1}{8}$. The focus - vertex relationship for a parabola $x=a(y - k)^2+h$ is given by the formula $(h +\frac{1}{4a},k)$.
Step2: Calculate the focus
Substitute $h=-2,a =-\frac{1}{8},k=-1$ into the focus formula. First, find $\frac{1}{4a}=\frac{1}{4\times(-\frac{1}{8})}=- 2$. Then $h+\frac{1}{4a}=-2-2=-4$. So the focus is $(-4,-1)$.
Step3: Determine the axis of symmetry
For a parabola of the form $x=a(y - k)^2+h$, the axis of symmetry is the line $y = k$. Since $k=-1$, the axis of symmetry is $y=-1$.
Step4: Find the directrix
The directrix of a parabola $x=a(y - k)^2+h$ is given by the equation $x=h-\frac{1}{4a}$. We know $h = - 2$ and $\frac{1}{4a}=-2$, so $x=-2-(-2)=-3$.
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Focus: $(-4,-1)$
Axis of Symmetry: $y=-1$
Directrix: $x=-3$