Finding..... Q (1 Viewer)

[Smile12345]

Hello All.

The question is...

(i) Find the coordinates of the focus and
(ii) the equation of the directrix of

a) x^2 - 6x - 4y - 3 = 0

I keep getting (3,-3) for i) but the answers have (3,-2)... Which is correct??

Could someone please help me???

Thanks in advance.

 

[HSC2014]

How do you find the vertex of that parabola? Then, once knowing the value of a, how do you find the focus?

 

[Smile12345]

Hmmmm.... I thought I'd done this... I'll put my working out here...

 

[Smile12345]

First ...

x^2 - 6x = 4y + 3

Then x^2 - 6x + 9 = 4y + 3 + 9

(x - 3)^2 = 4(y + 3)

From here I went .... (x - 3)^2 = 4(y - (-3) )

V: (3,-3)

Where have I gone wrong?

 

[HSC2014]

Yes, you have found the vertex - but what does the question ask you for?

 

[Smile12345]

Uh huh... The focus!! Thanks...