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Question

At how many points will the curves $y = x^2$ and $y = -x^2 - 2x - 1$ intersect in the real $(x, y)$ plane?

The correct answer is
0

Finding Curve Intersection Points

To find the points where the curves $y = x^2$ and $y = -x^2 - 2x - 1$ intersect, we set the expressions for $y$ equal to each other:

$x^2 = -x^2 - 2x - 1$

Solving the Quadratic Equation

Rearrange the equation to form a standard quadratic equation ($ax^2 + bx + c = 0$):

$x^2 + x^2 + 2x + 1 = 0$

$2x^2 + 2x + 1 = 0$

Using the Discriminant

We use the discriminant, $\Delta = b^2 - 4ac$, to determine the number of real solutions for $x$. A real solution corresponds to an intersection point.

  • If $\Delta > 0$, there are 2 real solutions (2 intersection points).
  • If $\Delta = 0$, there is 1 real solution (1 intersection point).
  • If $\Delta < 0$, there are no real solutions (0 intersection points).

For the equation $2x^2 + 2x + 1 = 0$, we have $a=2$, $b=2$, and $c=1$. Calculate the discriminant:

$\Delta = (2)^2 - 4(2)(1)$

$\Delta = 4 - 8$

$\Delta = -4$

Conclusion on Intersection Points

Since the discriminant $\Delta = -4$, which is less than 0, there are no real solutions for $x$. Therefore, the two curves do not intersect in the real $(x, y)$ plane.

The number of intersection points is 0.

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Important Questions from Co-ordinate Geometry

  1. The graphs of the linear equations 4x - 2y = 10 and 4x + ky = 2 intersect at a point (a, 4). The value of k is equal to:

  2. The area (in sq. units) of the triangle formed by the graphs of 8x + 3y = 24, 2x + 8 = y and the x-axis is:

  3. What is the area (in unit squares) of the triangle enclosed by the graphs of 2x + 5y = 12, x + y = 3 and the x-axis?

  4. The graphs of the equations 3x - 20y - 2 = 0 and 11x - 5y + 61 = 0 intersect at P(a, b). What is the value of (a 2+ b 2- ab)/(a 2- b 2+ ab)?

  5. The graphs of the linear equations 3x - 2y = 8 and 4x + 3y = 5 intersect at the point P(α, β). What is the value of (2 α - β)?

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