Chapter 5.5, Problem 1C

9. A 1 kg mass is attached to a spring with constant 13 N/m. The system is immersed in amedium which offers a damping force numerically equal to 6 times the instantaneous velocity.If x is the displacement of the mass from equilibrium, measured in meters,then x′′ + 6x′ + 13x = 0 . Which of the following statements is true?A. x(t) = c1e^−t + c2e^−5t, and the system is underdamped.B. x(t) = c1e^−t + c2e^−5t, and the system is overdamped.C. x(t) = c1e^−3t cos(2t) + c2e^−3t sin(2t), and the system is underdamped.D. x(t) = c1e^−3t cos(2t) + c2e^−3t sin(2t), and the system is overdamped.

Question 2 (A partial differential equation). The diffusion equation де Ət = 82 с მx2 where D is a positive constant, describes the diffusion of heat through a solid, or the concentration of a pollutant at time t at a distance x from the source of the pollution, or the invasion of alien species into a new habitat. Verify that the function c(x, t) -x²/(4Dt) = √4πDt is a solution of the diffusion equation.

13. Let y(x) be the solution to the initial value problem y′′ − 10y′ + 25y = 0, y(0) = 1, y′(0) = 3.Then y(1) = ? A. −e^5 B. 1 C. e^5 D. 4/5 e^5 + 1/5 e^−5 E. e^−5