Write the equation of a parabola given vertex and directrix

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Learn how to write the equation of a parabola given the vertex and the directrix. A parabola is the shape of the graph of a quadratic equation. A parabola can open up or down (if x is squared) or open left or right (if y is squared). Recall that the focus and the vertex of a parabola are on the same line of symmetry.

When given the vertex and the directrix of a parabola, recall that the vertex of a parabola is halfway between the focus and the directrix and the focus is inside the parabola. This enables us to identify the direction which the required parabola opens. We also need to identify the value of p, which is the distance between the vertex and the focus. p is negative when the parabola opens down or left and is positive when the parabola opens right or up.

Once we identify the direction and the value of p, we can use the equation of parabola given by (y - k)^2 = 4p(x - h) for parabolas that opens up or down and (x - h)^2 = 4p(y - k) for parabolas that opens left or right.
#conicsections #parabolaconicsections
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Better than my actual teacher thank you 🙏🏼

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I love you soooo much, my teacher does not know how to explain this and i'm rushing in time and you saved, God bless you sir.

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It's 2020 and I'm still here.

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My teacher can't even explain this well. I really Appreciate your way of teaching. Your students must be really lucky to have you.

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I've literally just binge watched your videos. They're really helpful.

heatherlee
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This was the exaxt question on the quiz bee I competed lol luckily i watched it haha thank you sir!

mikepineda
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Oh my god ive been confused the whole week and now i know how to do this one. Time to watch the others. Hopefully i dont get confused

parisht
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for some reason i understood this faster than my other math teacher

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Thank you. Your videos are always helpful.

ktmxcw
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Lol took me 30 seconds of viewing your video to understand what my teacher told us in 3 hours

kristiankieffer
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Great video and concrete information! Thanks.

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Thankyou so much you explained it so easily

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too all the people in cal 2 watching this, we thank you.

Admrilacbar
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what if vertex and directrex x? can you provide me a video?

syntaxerror
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I guess the equation of the parabola on the caption was interchange it should be left or right then up or down

aseanmingao
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2022 and I’m getting teaching that my teacher never gave me :)

cyrrus_lite