29–32. {Use of Tech} Errors in Euler’s method Consider the following initial value problems.
b. Using the exact solution given, compute the errors in the Euler approximations at t=0.2 and t=0.4.
y′(t) = −y, y(0) = 1; y(t) = e⁻ᵗ
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29–32. {Use of Tech} Errors in Euler’s method Consider the following initial value problems.
b. Using the exact solution given, compute the errors in the Euler approximations at t=0.2 and t=0.4.
y′(t) = −y, y(0) = 1; y(t) = e⁻ᵗ
42–43. Implicit solutions for separable equations For the following separable equations, carry out the indicated analysis.
b. Find the value of the arbitrary constant associated with each initial condition. (Each initial condition requires a different constant.)
y'(t) = t²/(y² + 1); y(−1) = 1, y(0) = 0, y(−1) = −1
Explain why or why not Determine whether the following statements are true and give an explanation or counterexample.
b. The solution of a stirred tank initial value problem always approaches a constant as t→∞
38–43. Equilibrium solutions A differential equation of the form y′(t)=f(y) is said to be autonomous (the function f depends only on y). The constant function y=y0 is an equilibrium solution of the equation provided f(y0)=0 (because then y'(t)=0 and the solution remains constant for all t). Note that equilibrium solutions correspond to horizontal lines in the direction field. Note also that for autonomous equations, the direction field is independent of t. Carry out the following analysis on the given equations.
b. Sketch the direction field, for t≥0.
y′(t) = 2y + 4
38–43. Equilibrium solutions A differential equation of the form y′(t)=f(y) is said to be autonomous (the function f depends only on y). The constant function y=y0 is an equilibrium solution of the equation provided f(y0)=0 (because then y'(t)=0 and the solution remains constant for all t). Note that equilibrium solutions correspond to horizontal lines in the direction field. Note also that for autonomous equations, the direction field is independent of t. Carry out the following analysis on the given equations.
b. Sketch the direction field, for t≥0.
y′(t) = 6 - 2y
27–30. Predator-prey models Consider the following pairs of differential equations that model a predator-prey system with populations x and y. In each case, carry out the following steps.
b. Find the lines along which x'(t) = 0. Find the lines along which y'(t) = 0.
x′(t) = 2x − xy, y′(t) = −y + xy