Aparabola has its focus at (0, 3) and its directrix at x = 4. 3a. what are the coordinates of the vertex? 3b. what is the focal length of the parabola? 3c. what is the equation, in standard form, of the parabola? i want some with understanding this, i'm very confused and annoyed

a. The coordinates of the vertex are (2 , 3)

b. The focal length of the parabola is 8

c. The equation, in standard form, of the parabola is (y - 3)² = -8(x - 2)²

Step-by-step explanation:

* Lets revise the equation of a parabola  

- If the equation is in the standard form (y − k)² = 4p(x − h), then:

# Use the given equation to identify h and k for the vertex, (h , k)

# Use the value of k to determine the axis of symmetry, y = k

# Use h , k and p to find the coordinates of the focus, (h + p , k)

# Use h and p to find the equation of the directrix, x = h − p

# The endpoints of the focal diameter,  (h + p , k ± 2p)

# The focal length is I4pI

* Now lets solve the problem

∵ The parabola has focus at (0 , 3)

∵ The coordinates of its focus, (h + p , k)

∴ h + p = 0 ⇒ (1)

∴ k = 3

∵ Its directrix at x = 4

∵ The equation of the directrix, x = h − p

∴ h - p = 4 ⇒ (2)

- Add (1) and (2) to find h and p

∴ h + p + h - p = 0 + 4 ⇒ add the like terms

∴ 2h = 4 ⇒ divide both sides by 2

∴ h = 2

- Substitute the value of h in (1)

∴ 2 + p = 0 ⇒ subtract 2 from both sides

∴ p = -2

a. ∵ h = 2 and k = 3

∵ The vertex of the parabola is (h , k)

∴ The coordinates of the vertex are (2 , 3)

b. ∵ The focal length is I4pI

∵ p = -2

∴ The focal length = I4 × -2I = I-8I = 8

∴ The focal length of the parabola is 8

c. ∵ The equation in the standard form is (y − k)² = 4p(x − h)

∵ h = 2 , k = 3 , p = -2

∴ The equation is (y - 3)² = 4(-2)(x - 2)²

∴ The equation is (y - 3)² = -8(x - 2)²

∴ The equation, in standard form, of the parabola is (y - 3)² = -8(x - 2)²