Geometry · real student question

For the parabola (x - 1)^2 = 8(y - 2), identify the vertex, focus, axis of symmetry, and directrix.

Question

Identify the vertex, focus, axis of symmetry and directrix of the parabola

(x1)2=8(y2).(x-1)^2=8(y-2).

Step-by-step solution

  1. Match the equation to a standard form. The squared variable is xx, so this is a vertical parabola and the template is (xh)2=4p(yk)(x-h)^2=4p(y-k). Which variable is squared decides the whole orientation, so identify it before anything else.

  2. Read off h, k and 4p. Comparing (x1)2=8(y2)(x-1)^2=8(y-2) with the template gives h=1h=1, k=2k=2 and 4p=84p=8, hence p=2p=2. Because p>0p>0, the parabola opens upward.

  3. State the vertex. The vertex is (h,k)=(1,2)(h,k)=(1,2); it is the point where the squared term is zero.

  4. Locate the focus. For a vertical parabola the focus sits pp units from the vertex along the axis, in the direction of opening: (h,k+p)=(1,2+2)=(1,4)(h,k+p)=(1,2+2)=(1,4).

  5. Write the axis of symmetry and directrix. The axis is the vertical line through the vertex, x=h=1x=h=1. The directrix is the horizontal line pp units on the opposite side: y=kp=22=0y=k-p=2-2=0, which is the xx-axis here.

  6. Check with the focus-directrix definition. Take the point (5,4)(5,4), which satisfies (51)2=16=8(42)(5-1)^2=16=8(4-2). Its distance to the focus (1,4)(1,4) is 44, and its distance to the line y=0y=0 is also 44. Equal distances confirm the focus and directrix.

Answer

Vertex (1,2), focus (1,4), axis x=1, directrix y=0\text{Vertex } (1,2),\ \text{focus } (1,4),\ \text{axis } x=1,\ \text{directrix } y=0

Need to solve a different problem like this? Open the solver →