Find Min Distance b/w Parabolas: 7/(4*root2)

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In summary, using concepts from parabolas, the minimum distance between the curves y^2 - xy - 2x^2 = 0 and y^2 = x - 2 can be found by splitting the first equation into two linear factors and drawing a graph. It can be determined that the line y=-x is closer, and using the slope form of tangent to a parabola, the distance between the two parallel lines can be calculated to be 7/(4*root2).
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erisedk
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Homework Statement


Find the minimum distance between the curves y^2 - xy - 2x^2 = 0 and y^2 = x - 2.
Ans: 7/(4*root2)

Homework Equations

The Attempt at a Solution


It's supposed to be done using concepts from parabolas. I tried using calc but it got convoluted.
 
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  • #2
erisedk said:

Homework Statement


Find the minimum distance between the curves y^2 - xy - 2x^2 = 0 and y^2 = x - 2.
Ans: 7/(4*root2)

Homework Equations

The Attempt at a Solution


It's supposed to be done using concepts from parabolas. I tried using calc but it got convoluted.

y^2 - xy - 2x^2 splits into two linear factors. That makes it easier since the graph becomes two lines.
 
  • #3
Ohhh ok. I didn't realize that was a pair of straight lines.
I did it now. Split it into y=-x and y=2x. Drew a rough graph. It's clear from the graph that y=-x is closer. So, using the slope form of tangent to a parabola, I wrote the equation of tangent with the slope -1, and figured out the distance between the two parallel lines, which comes out to be the answer. Thanks :D
 

1. What is the equation for a parabola?

A parabola is a type of curve that is formed by the graph of a quadratic equation, y = ax^2 + bx + c, where a, b, and c are constants.

2. How do you find the minimum distance between two parabolas?

To find the minimum distance between two parabolas, we can use the distance formula. We first set the two parabolas equal to each other to find the points of intersection. Then, we can use the distance formula to find the distance between these points, which will give us the minimum distance between the two parabolas.

3. What is the significance of the number 7 in the equation 7/(4*root2)?

The number 7 indicates the y-coordinate of the vertex of the parabola. In the equation y = ax^2 + bx + c, the vertex has coordinates (-b/2a, c - b^2/4a). Since there is no x-term in the given equation, the x-coordinate of the vertex is 0, and the y-coordinate is 7.

4. How can you tell if two parabolas intersect?

If the two parabolas have different coefficients for their x^2 terms, then they will intersect at two points. If the coefficients are the same, then the two parabolas are either identical or parallel and will not intersect. This can be determined by setting the two equations equal to each other and solving for x.

5. Can the minimum distance between two parabolas ever be 0?

Yes, the minimum distance between two parabolas can be 0 if the two parabolas are identical. In this case, they would intersect at every point and have a minimum distance of 0.

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