Chapter 5: Q2E (page 249)
Show that the operator (D-1)(D+2) is the same as the operator .
Short Answer
Thus, it is proved that theoperator is the same as the operator
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Chapter 5: Q2E (page 249)
Show that the operator (D-1)(D+2) is the same as the operator .
Thus, it is proved that theoperator is the same as the operator
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In Problems 19–24, convert the given second-order equation into a first-order system by setting v=y’. Then find all the critical points in the yv-plane. Finally, sketch (by hand or software) the direction fields, and describe the stability of the critical points (i.e., compare with Figure 5.12).
Secretion of Hormones.The secretion of hormones into the blood is often a periodic activity. If a hormone is secreted on a 24-h cycle, then the rate of change of the level of the hormone in the blood may be represented by
the initial value problem\(\frac{{{\bf{dx}}}}{{{\bf{dt}}}}{\bf{ = \alpha - \beta cos}}\frac{{{\bf{\pi t}}}}{{{\bf{12}}}}{\bf{ - kx,x(0) = }}{{\bf{x}}_{\bf{o}}}\)where x(t) is the amount of the hormone in the blood at the time t, \({\bf{\alpha }}\) is the average secretion rate, \({\bf{\beta }}\)is the amount of daily variation in the secretion, and kis a positive constant reflecting the rate at which the body removes the hormone from the blood. If \({\bf{\alpha }}\)=\({\bf{\beta }}\) = 1, k= 2, and \({{\bf{x}}_{\bf{o}}}\) = 10, solve for x(t).
For the interconnected tanks problem of Section5.1, page241, suppose that instead of pure water being fed into the tankA, a brine solution with concentration is used; all other data remain the same. Determine the mass of salt in each tank at time if the initial masses are and .
Feedback System with Pooling Delay. Many physical and biological systems involve time delays. A pure time delay has its output the same as its input but shifted in time. A more common type of delay is pooling delay. An example of such a feedback system is shown in Figure 5.3 on page 251. Here the level of fluid in tank B determines the rate at which fluid enters tank A. Suppose this rate is given by where and V are positive constants and is the volume of fluid in tank B at time t.

b. Find a general solution for the system in part (a) when and .
c. Using the general solution obtained in part (b), what can be said about the volume of fluid in each of the tanks as ?
Generalized Blasius Equation. H. Blasius, in his study of the laminar flow of a fluid, encountered an equation of the form . Use the Runge–Kutta algorithm for systems with h = 0.1 to approximate the solution that satisfies the initial conditions . Sketch this solution on the interval [0, 2].
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