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Ch. 9 - Differential Equations
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Briggs 3rd EditionCh. 9 - Differential Equations문제 9.3.54a
9장, 문제 9.3.54a

[Use of Tech] Analysis of a separable equation Consider the differential equation yy'(t) = ½eᵗ + t and carry out the following analysis.
a. Find the general solution of the equation and express it explicitly as a function of t in two cases: y > 0 and y < 0.

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Rewrite the given differential equation \(y y'(t) = \frac{1}{2} e^{t} + t\) by recognizing that \(y'(t) = \frac{dy}{dt}\). This gives \(y \frac{dy}{dt} = \frac{1}{2} e^{t} + t\).
Separate variables by multiplying both sides by \(dt\) and dividing both sides by \(y\): \(y \, dy = \left( \frac{1}{2} e^{t} + t \right) dt\).
Integrate both sides: \(\int y \, dy = \int \left( \frac{1}{2} e^{t} + t \right) dt\). This will give you an implicit relation between \(y\) and \(t\).
Compute the integrals separately: \(\int y \, dy = \frac{y^{2}}{2} + C_1\) and \(\int \left( \frac{1}{2} e^{t} + t \right) dt = \frac{1}{2} e^{t} + \frac{t^{2}}{2} + C_2\). Combine constants into a single constant \(C\).
Solve for \(y\) explicitly by multiplying both sides by 2 and taking the square root: \(y = \pm \sqrt{e^{t} + t^{2} + C}\). Then express the general solution separately for \(y > 0\) and \(y < 0\) as \(y = +\sqrt{e^{t} + t^{2} + C}\) and \(y = -\sqrt{e^{t} + t^{2} + C}\) respectively.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Separable Differential Equations

A separable differential equation can be written as a product of a function of y and a function of t, allowing variables to be separated on opposite sides of the equation. This enables integration with respect to each variable independently to find the general solution.
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06:06
Solving Separable Differential Equations

Integration of Both Sides

After separating variables, integrating both sides is essential to solve for y explicitly. This involves integrating functions of t on one side and functions of y on the other, often requiring techniques like substitution or recognizing standard integral forms.
추천 영상:
05:50
One-Sided Limits

Handling Absolute Values and Sign Cases

When solving for y explicitly, the solution may involve absolute values due to integration of terms like 1/y. Distinguishing cases y > 0 and y < 0 ensures correct interpretation of the solution and avoids ambiguity in the sign of y.
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가이드 코스
05:59
Initial Value Problems Example 2
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교과서 질문

Explain why or why not Determine whether the following statements are true and give an explanation or counterexample.

a. The general solution of the differential equation y'(t) = 1 is y(t) = t

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교과서 질문

17–20. Increasing and decreasing solutions Consider the following differential equations. A detailed direction field is not needed.


a. Find the solutions that are constant, for all t ≥ 0 (the equilibrium solutions).


y'(t) = (y−2)(y+1)

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교과서 질문

33–36. {Use of Tech} Computing Euler approximations Use a calculator or computer program to carry out the following steps.

a. Approximate the value of y(T) using Euler’s method with the given time step on the interval [0,T].


y′(t) = -2y, y(0) = 1; Δt = 0.2, T = 2; y(t) = e⁻²ᵗ

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교과서 질문

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.

a. Find the equilibrium solutions.


y′(t) = 2y + 4

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46–48. Analyzing models The following models were discussed in Section 9.1 and reappear in later sections of this chapter. In each case, carry out the indicated analysis using direction fields.

Drug infusion The delivery of a drug (such as an antibiotic) through an intravenous line may be modeled by the differential equation m′(t)+km(t)=I, where m(t) is the mass of the drug in the blood at time t≥0, K is a constant that describes the rate at which the drug is absorbed, and I is the infusion rate. Let I=10mg/hr and k=0.05 hr^−1.

a. Draw the direction field, for 0≤t≤100, 0≤y≤600.

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교과서 질문

Consider the differential equation y'(t)+9y(t)=10.

a. How many arbitrary constants appear in the general solution of the differential equation?

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