Intersection of a line and circle

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SUMMARY

The intersection of the line defined by the equation x + y = 2a - 1 and the circle given by x² + y² = a² + 3a - 3 is analyzed to find the value of 'a' that minimizes the product m*n at the intersection point (m,n). By squaring the linear equation and utilizing the identity (x+y)² = x² + y² + 2xy, the term x² + y² can be eliminated from the equations. This results in expressing xy as a function of 'a', leading to a straightforward solution for determining the optimal value of 'a'.

PREREQUISITES
  • Understanding of linear equations and their graphical representation
  • Familiarity with circle equations in Cartesian coordinates
  • Knowledge of algebraic manipulation, including squaring equations
  • Basic concepts of optimization in mathematics
NEXT STEPS
  • Study the method of Lagrange multipliers for optimization problems
  • Learn about the properties of conic sections, specifically circles
  • Explore algebraic techniques for eliminating variables in equations
  • Investigate the application of calculus in finding minima and maxima
USEFUL FOR

Students in mathematics, particularly those studying algebra and geometry, as well as educators looking for examples of intersection problems involving lines and circles.

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Homework Statement



The line x+y=2a-1 intersects the circle x2+y2=a2+3a-3 at point (m,n). When m*n reaches its minimum value, what is the value of a?

Homework Equations



Equation One

x + y = 2a - 1

Equation Two

x2 + y 2 = a 2 + 3a - 3
 
Last edited:
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Square your linear (first) equation, using the fact that (x+y)^2 = x^2 + y^2 + 2xy, at which point you can easily eliminate "x^2 + y^2" from the two equations. Now you have "xy" as a function of "a" and the rest should be easy.
 

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