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Appendix F Selected Hints

1 What is a Differential Equation?
1.5 Exercises
πŸ‹οΈβ€β™‚οΈ Practice Drills

Exercises

1. Identify the Differential Equations.
1.a
Hint.
There are only four differential equations in this set.
3. Identify the Coefficients.
3.b
Hint.
Look for the dependent variable in each term. The coefficient is the constant or function that multiplies the dependent variable.

2 Classification
2.4 Exercises
πŸ‹οΈβ€β™‚οΈ Practice Drills

Exercises

2. Identify the Linear & Nonlinear Differential Equations.
2.f
Hint.
Remember that a linear differential equation contains only linear terms. Four of these equations are linear.
2.g
Hint.
First, identify the dependent variable, then carefully examine each term to determine whether it is nonlinear.

5 Separation of Variables
5.5 Exercises
πŸ’‘ Conceptual Quiz

Exercises

1. True or False.
1.i πŸ‘πŸ‘Ž.
Hint.
Check that the differential equation is first-order and separable.
1.j πŸ‘πŸ‘Ž.
Hint.
Check that the differential equation is first-order and separable.

6 Integrating Factor
6.1 Exercises

πŸ’‘ Conceptual Quiz

6.1.1.
6.1.1.a πŸ‘πŸ‘Ž.
Hint.
Check to see that the differential equation is in the form \(y'+P(x)y=Q(x)\text{.}\)

πŸ‹οΈβ€β™‚οΈ Practice Drills

6.1.1. Identifying Equations for the IF Method.
Hint.
A first-order linear equation has \(y\) and \(y'\) only to the first power and not inside nonlinear functions.

8 Euler’s Method
8.4 Exercises

✍🏻 Problems

8.4.1.
Hint.
Start with the given initial condition \(y_0 = -1\) at \(x_0 = 0\text{.}\) Use Euler’s update formula: \(y_{k+1} = y_k + h \cdot f(x_k, y_k)\text{,}\) where \(f(x, y) = y^2 - x\text{.}\) You’ll need to compute two steps to reach \(x = 1\text{.}\)

9 Homogeneous Equations (LHCC)
9.6 Exercises

πŸ‹οΈβ€β™‚οΈ Practice Drills

9.6.1. Identifying LHCC Equations.
9.6.1.f Select the LHCC Equations.
Hint.
There are only 4 LHCC equations in this set.