# Find the equaion of the parabola

1. Apr 20, 2010

### r-soy

Find the equaion of the parabola having its vertex at the origin , its axis as indicated :

A ) x-axis : (-4, - 20 )

b) y - axis : (30,-15 )

C) y - axis : (-root2,3)

my answer

A )

we have (-4, - 20 ) that mean the focus ( - 20 , 0 )

now we do comper 4ay = - 20

= -5

then the equation is : y2 = 4ax

= y2 =4(-5) x

=y2 = -20 x

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I sove only number one beacuse i am not sure from my answer

help me Are this solving corect or not ?

2. Apr 20, 2010

### r-soy

I want you ?

3. Apr 20, 2010

### Staff: Mentor

These aren't very clear. I guess you mean the axis of symmetry (x-axis or y-axis) and a point on the parabola.
Why do you think the focus is at (-20, 0)?
What equals -5?
y2 = 4ax is the right equation form, but you don't have the right value for a. The point (-4, -20) should make your equation a true statement, but (-20)2 $\neq$ -20(-4).

You need to get into the habit of checking your work.

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