Math Problem Statement

The line with equation y = 2x + 1 meets the curve with equation kx^2 + 2y + (k - 2) = 0 at exactly one point. Given that k is a positive constant, find the value of k.

Solution

The problem asks us to find the value of kk, given that the line y=2x+1y = 2x + 1 meets the curve with the equation kx2+2y+(k2)=0kx^2 + 2y + (k - 2) = 0 at exactly one point, and that kk is a positive constant.

Step-by-step solution:

  1. Substitute the line equation into the curve equation: Since the line intersects the curve, we substitute y=2x+1y = 2x + 1 into the curve equation kx2+2y+(k2)=0kx^2 + 2y + (k - 2) = 0.

    kx2+2(2x+1)+(k2)=0kx^2 + 2(2x + 1) + (k - 2) = 0

  2. Expand the terms: kx2+4x+2+k2=0kx^2 + 4x + 2 + k - 2 = 0 Simplify the constants: kx2+4x+k=0kx^2 + 4x + k = 0

  3. Solve for the condition of exactly one point: The condition that the line meets the curve at exactly one point means that the quadratic equation must have exactly one solution. This happens when the discriminant is zero.

    The discriminant of a quadratic equation ax2+bx+c=0ax^2 + bx + c = 0 is given by: Δ=b24ac\Delta = b^2 - 4ac For the equation kx2+4x+k=0kx^2 + 4x + k = 0, we have:

    • a=ka = k
    • b=4b = 4
    • c=kc = k

    The discriminant is: Δ=424(k)(k)\Delta = 4^2 - 4(k)(k) Simplifying: Δ=164k2\Delta = 16 - 4k^2

  4. Set the discriminant equal to zero: To ensure exactly one solution, we set the discriminant equal to zero: 164k2=016 - 4k^2 = 0 Solve for kk: 4k2=164k^2 = 16 k2=4k^2 = 4 k=2k = 2 Since kk is given as a positive constant, the value of kk is 22.

Thus, the value of kk is 2\boxed{2}.


Would you like more details or have any questions?

Here are 5 related questions to expand your understanding:

  1. What would happen if the discriminant were positive or negative?
  2. How do we determine if two curves intersect at more than one point?
  3. Can this method be applied to any curve and line intersection?
  4. How would the solution change if the curve had a different general form, like kx2+3y+(k5)=0kx^2 + 3y + (k - 5) = 0?
  5. What if the line equation was y=mx+by = mx + b instead of y=2x+1y = 2x + 1?

Tip: The discriminant is key in determining how many solutions a quadratic equation has, making it essential in problems involving intersections between curves and lines.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Intersection of Lines and Curves

Formulas

Quadratic equation: ax^2 + bx + c = 0
Discriminant formula: Δ = b^2 - 4ac

Theorems

Discriminant of a quadratic equation

Suitable Grade Level

Grades 10-12