Melody

Thanks alan, I think that is all a bit too much for me.

 Never mind, maybe I will work it out some time in the future.   

Thank you Alan.   

if 7x=35 then x=5 

Your answer is correct.

theirs is wrong.    

It is just

$$\frac{-x}{2}$$

thanks Chris,

One day I will get the time to 'study' your vector answers.    

This is a sideways parabola

$$\\3y^2-4x=0\\\\
y^2=\frac{4x}{3}\\\\
y^2=4 \times \frac{1}{3}\times x\\\\$$

Focal length = 1/3

focus (1/3, 0)

Laus r****m is 4*1/3 long = 4/3

The ends of it will be (1/3, 2/3) and (1/3, -2/3)

it was 88 over 28 unknown but your logic is correct.

Have a look at this page.