In the xy-plane, a line that has the equation y = c for some constant c intersects a parabola at exactly one point . If the parabola has the equation y=-x^ 2 +5x. what is the value of c?

Respuesta :

Answer:

c=6.25

Step-by-step explanation:

If a line that is flat (has a slope of zero) hits only one point of the parabola, it means that point is the vertex of the parabola.

In this case your equation is ---

y= –x^2 + 5x

--- and you just need to write in vertex for the equation:

y=a(x–h)^2 + k

y= –(x–2.5)^2 + 6.25

The vertex is (h,k) or (2.5,6.25)

Since the equation is "y=", k=c

or c=6.25

Thank You.

In this question:

  • We have to find the point of intersection of the line and the parabola.
  • To do this, we have to apply concepts needed to solve a quadratic equation.

Doing this, we find that the value is: [tex]c = \frac{25}{4}[/tex]

Solving a quadratic equation:

Given a second order polynomial expressed by the following equation:

[tex]ax^{2} + bx + c, a\neq0[/tex].

This polynomial has roots [tex]x_{1}, x_{2}[/tex] such that [tex]ax^{2} + bx + c = a(x - x_{1})*(x - x_{2})[/tex], given by the following formulas:

[tex]x_{1} = \frac{-b + \sqrt{\Delta}}{2*a}[/tex]

[tex]x_{2} = \frac{-b - \sqrt{\Delta}}{2*a}[/tex]

[tex]\Delta = b^{2} - 4ac[/tex]

Line: y = c

Parabola: y = -x^ 2 +5x.

The intersection is at the point:

[tex]-x^2 + 5x = c[/tex]

[tex]-x^2 + 5x - c = 0[/tex]

[tex]x^2 - 5x + c = 0[/tex]

Which is a quadratic equation with [tex]a = 1, b = -5[/tex].

The line and the parabola intersect at exactly one point, which means that the quadratic equation has one solution, that is, [tex]\Delta = 0[/tex].

Since:

[tex]\Delta = b^{2} - 4ac[/tex]

It means that:

[tex]b^2 - 4ac = 0[/tex]

We use this to find the value of c.

[tex](-5)^2 - 4(1)(c) = 0[/tex]

[tex]4c = 25[/tex]

[tex]c = \frac{25}{4}[/tex]

The value is: [tex]c = \frac{25}{4}[/tex]

A similar question is found at https://brainly.com/question/15211279

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