What is the equation of a parabola with a focus of (8,2) and a directrix of x=6?

1. 4(x-7)=(y-2)²
2. 4(x+7)=(y+2)²
3. 4(x-2)=(y-7)²
4. 4(x+2)=(y+7)²

Please show work!!

Respuesta :

distance of a point (x,y) from focus = its distance from the directrix so

sqrt[(x-8)^2 + (y - 2)^2] = x - 6

squaring both sides:-

x^2 - 16x + 64 + y^2 -4y + 4 = x^2 -12x + 36

y^2 - 4y  = 4x - 32

(y-2)^2 - 4 = 4x - 32

(y - 2)62 = 4x - 28

(y - 2)^2 = 4(x - 7)

No. 1 is the correct choice


The equation of parabola with a focus of (8,2) and a directrix of x = 6 is [tex]\bold{(y-2)^2=4(x-7)}[/tex]

What is the equation of parabola?

"It is a plane curve generated by moving a point so that its distance from a fixed point is equal to its distance from a fixed line."

What is focus of parabola?

"The fixed point is the focus of parabola"

What is directrix?

"The fixed-line is the directrix of the parabola."

What is the distance between two points?

"The distance between two points [tex](x_1,y_1),(x_2,y_2)[/tex] is,

[tex]d=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}[/tex]"

For given question,

We know, parabola is a curve whose distance from a fixed point is equal to its distance from a fixed line.

We have been given a focus of (8, 2) and a directrix of x = 6

Using distance formula the distance from a fixed point would be,

[tex]d=\sqrt{(x-8)^2+(y-2)^2}[/tex]

And the distance from a fixed line would be,

d1 = x - 6

distance from a fixed point = distance from a fixed line

⇒ [tex]\sqrt{(x-8)^2+(y-2)^2}=x-6[/tex]

⇒ [tex](x-8)^2+(y-2)^2=(x-6)^2[/tex]            ..........(squaring on both the sides)

⇒ [tex]x^{2} -16x+64+(y-2)^2=x^{2} -12x+36[/tex]

⇒ [tex](y-2)^2=x^{2} -12x+36-x^{2} +16x-64[/tex]

⇒ [tex](y-2)^2=4x-28[/tex]

⇒ [tex]\bold{(y-2)^2=4(x-7)}[/tex]

Therefore, the equation of parabola with a focus of (8,2) and a directrix of x = 6 is [tex]\bold{(y-2)^2=4(x-7)}[/tex]

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