1. **Problem Statement:** Find the coordinates of the foci, the equations of the directrices, and the length of the latus rectum for each parabola.
2. **General formulas for parabolas:**
- For a parabola of the form $y^2 = 4ax$, the focus is at $(a,0)$, the directrix is $x = -a$, and the length of the latus rectum is $4a$.
- For a parabola of the form $x^2 = 4ay$, the focus is at $(0,a)$, the directrix is $y = -a$, and the length of the latus rectum is $4a$.
3. **Apply to each parabola:**
(i) $y^2 = 8x$
- Rewrite as $y^2 = 4(2)x$, so $a=2$.
- Focus: $(2,0)$
- Directrix: $x = -2$
- Length of latus rectum: $4 \times 2 = 8$
(ii) $x^2 = 6y$
- Rewrite as $x^2 = 4(\frac{3}{2})y$, so $a=\frac{3}{2}$.
- Focus: $(0, \frac{3}{2})$
- Directrix: $y = -\frac{3}{2}$
- Length of latus rectum: $4 \times \frac{3}{2} = 6$
(iii) $y^2 = -12x$
- Rewrite as $y^2 = 4(-3)x$, so $a = -3$ (parabola opens left).
- Focus: $(-3,0)$
- Directrix: $x = 3$
- Length of latus rectum: $4 \times 3 = 12$
(iv) $x^2 = 16y$
- Rewrite as $x^2 = 4(4)y$, so $a=4$.
- Focus: $(0,4)$
- Directrix: $y = -4$
- Length of latus rectum: $4 \times 4 = 16$
**Final answers:**
(i) Focus: $(2,0)$, Directrix: $x=-2$, Latus rectum length: $8$
(ii) Focus: $(0, \frac{3}{2})$, Directrix: $y=-\frac{3}{2}$, Latus rectum length: $6$
(iii) Focus: $(-3,0)$, Directrix: $x=3$, Latus rectum length: $12$
(iv) Focus: $(0,4)$, Directrix: $y=-4$, Latus rectum length: $16$
Parabola Properties 1815B4
Step-by-step solutions with LaTeX - clean, fast, and student-friendly.