1550078481-Ordinary_Differential_Equations__Roberts_

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432 Ordinary Differential Equations

E X ERCISES 10.2

I n exercises 1 -8 calculate the eigenvalues of the given linear sys-

tem. Indicate whether the critical point is asymptotically stable,

neutrally stable, or unstable. Specify if the critical point is a node,

saddle point, spiral point, or center.


  1. x ' = -2x + 3y 2. x ' = -x+2y


y' = - x + 2y y' = - 2x + 3y

3. x' = x - 2y 4. x ' = - x - 2y

y' = 2x - 3y y' = 5x + y


  1. x ' = -x+2y 6. x' = x - 2y


y' = -2x -y y' = 2x+ y



  1. x' = -5x -y + 2 8. x' = 3x-2y- 6


y' = 3x -y- (^3) y' = 4x-y + 2


In exercises 9- 15 find all real critical points. Compute the eigen-

values of the associated linear system at each critical point. Deter-

mine if the critical point is stable or unstable and, when possible,

specify its type (node, saddle point, or spiral point).

9. x' = -x + x y 10. x ' = x +y


y' = -y + xy y' = Y + x2



  1. x' = -x+xy 12. x' = x + 1


y' = y-2xy y' = 1-y 2


13. x ' = y2 - x2 1 4. x ' = y-xy


y' = 1 -x y' = y2 _ x2



  1. x ' = -x+xy


y' = y-xy + y2

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