Find the equaion of the parabola

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r-soy
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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 ?
 
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r-soy said:
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)
These aren't very clear. I guess you mean the axis of symmetry (x-axis or y-axis) and a point on the parabola.
r-soy said:
my answer



A )

we have (-4, - 20 ) that mean the focus ( - 20 , 0 )
Why do you think the focus is at (-20, 0)?
r-soy said:
now we do comper 4ay = - 20

= -5
What equals -5?
r-soy said:
then the equation is : y2 = 4ax

= y2 =4(-5) x

=y2 = -20 x
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 [itex]\neq[/itex] -20(-4).

You need to get into the habit of checking your work.
r-soy said:
----------------



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

help me Are this solving corect or not ?