How to find the equation of a parabola.

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In summary, the conversation discusses finding the equation of a parabola given certain information, such as the x-intercepts, y-intercept, and vertex. The equation must be in the standard form of y = ax^2 + bx + c. The attempt at a solution involves putting the equation in the form of y = a(x - p)^2 + q and then expanding it to match the standard form. The values of a, b, and c can be determined from the expanded expression. Ultimately, the conversation ends with the problem being solved and the individual thanking the expert for their help.
  • #1
john_blah
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Homework Statement


Find the equation of the parabola if you have the following information:
Xintersects: (-4;0) and (0;0)
Yint: y = 7
Vertex: (-2;7)



Homework Equations


The equation must be in the standard form:
y=ax^2 + bx + c


The Attempt at a Solution


I know how to put it into the equation y = a(x^2 - p) + q but I have no idea how to put it into the y=ax^2 + bx + c form, which is asked.


Thanks
 
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  • #2
john_blah said:

Homework Statement


Find the equation of the parabola if you have the following information:
Xintersects: (-4;0) and (0;0)
Yint: y = 7
Vertex: (-2;7)



Homework Equations


The equation must be in the standard form:
y=ax^2 + bx + c


The Attempt at a Solution


I know how to put it into the equation y = a(x^2 - p) + q but I have no idea how to put it into the y=ax^2 + bx + c form, which is asked.


Thanks
I think you mean you know how to put it in the form y = a(x - p)2 + q. Why not put it in this form and then expand the right hand side so it looks like y=ax2+bx+c?
 
  • #3
Alright but unfortunately I have got no idea how to do that. Could you please elaborate?
 
  • #4
Expand the right hand side to give y=a(x2-2px+p2)+q. Now can you spot the value of a,b and c in y=ax2+bx+c from this above expression?
 
  • #5
Oh my word I can't believe I did not see that before!

Thank you! :rofl:
 

1. What is a parabola?

A parabola is a type of curve that is formed when a plane intersects with a cone at a particular angle. It is a U-shaped curve that can be seen in many real-life situations, such as the trajectory of a thrown ball or the shape of a satellite dish.

2. How do you find the equation of a parabola?

The equation of a parabola can be found using the general form: y = ax^2 + bx + c, where a, b, and c are constants. To find these values, you will need to know the coordinates of at least three points on the parabola or have information about the focus and directrix of the parabola.

3. What is the focus and directrix of a parabola?

The focus of a parabola is a fixed point on the curve that is equidistant from any point on the parabola and the directrix, which is a fixed line parallel to the axis of symmetry. These two elements are important in determining the shape and position of a parabola.

4. Can a parabola have a negative coefficient for the x^2 term?

Yes, a parabola can have a negative coefficient for the x^2 term. This will result in a downward-facing parabola instead of the typical upward-facing parabola. The sign of the coefficient affects the direction in which the parabola opens.

5. Are there different types of parabolas?

Yes, there are different types of parabolas, such as standard, vertex, and intercept form. These different forms allow for easier graphing and interpretation of the parabola's features, such as its vertex, focus, and directrix.

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