Find the vertex, given two points on the parabola and....

[osoriopinto5]

I really need some help. I don't know if this has been posted already, but please help.

A parabola passes thru points (5,1) and (13,-7) and has y-axis as directrix. What are values of vertex?

Thank you!

 

[stapel]

If the y-axis is the directrix, what then is the general form of the quadratic? (This should be one of the formulas they gave you.)

Eliz.

 

[osoriopinto5]

Well, I'm taking AlgebraII and I don't know much about trig. That's why I need some help in solving this problem. I need to learn it to prepare for math competitions.

Thanks

 

[pka]

Well, I'm taking AlgebraII and I don't know much about trig. That's why I need some help in solving this problem. I need to learn it to prepare for math competitions.

But this question is not about trigonometry!
It is a standard algebra question.
Look up “parabola” in your text. This one opens to the right.

 

[osoriopinto5]

It really didnt say much.Can you at least tell me how to get stared o the problem?

 

[stapel]

Can you at least tell me how to get stared on the problem?

Look up the section on "parabolas" in your text. Review the formulas they gave you. (These formulas differ from book to book, so you'll need to tell us what you're using.)

Relate the given directrix information to the formulas, to get the general form of the quadratic. Then try plugging in the given points, and see what this gives you.

Eliz.

P.S. The second thread you started on this question has been deleted. Please post your replies, including your work, to this originating thread. Thank you.

 

[osoriopinto5]

Can you give me an example? How do you put the y axis in a formula. I see this formula

y=a(x-h)^2+k

Is that right?

 

[stapel]

Can you give me an example?

We really can't teach courses here. If you're needing instruction, explanation, and worked examples, please specify, so we can try to find links for you. Thank you.

I see this formula: y=a(x-h)^2+k Is that right?

If you mean "does this apply to this particular exercise?", then no. This would be the formula they gave you for parabolas having the x-axis (or lines parallel to it) as the directrix. As was mentioned earlier, your parabola is "sideways", and thus would use the other formula the book gave you.

Eliz.