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Solve the following problems. $$y^{\prime}(t)=\left(2 t^{2}+4\right) / t, y(1)=2$$

Short Answer

Expert verified
Answer: The function y(t) that satisfies the given differential equation and initial condition is y(t) = t^2 + 4ln|t| + 1.

Step by step solution

01

Integrate the given differential equation

To find y(t), we need to integrate y'(t) with respect to t. $$\int y'(t) \, dt = \int \frac{2t^2 + 4}{t} \, dt$$ Now, let's simplify the integral. $$= \int (2t + \frac{4}{t}) \, dt$$
02

Integrate each term

Integrate each term separately. $$\int (2t + \frac{4}{t}) \, dt = \int 2t \, dt + \int \frac{4}{t} \, dt$$ Now, we find the antiderivatives for each term. $$=\left[t^2\right]+\left[4\ln|t|\right]+C$$
03

Combine terms

Combine the terms back together. $$y(t)=t^2 +4\ln|t|+C$$
04

Apply the initial condition

In this step, we need to use the initial condition y(1)=2 to find the value of C. $$2=1^2+4\ln|1|+C$$ Since ln(1)=0, the equation simplifies to: $$2=1+C$$
05

Solve the initial condition for C

Now, solve the initial condition equation for C. $$C=1$$
06

Write the final solution

Replace C with the value found in the previous step and write the final solution for y(t). $$y(t)=t^2+4\ln|t|+1$$

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Initial Value Problem
An Initial Value Problem (IVP) is a type of differential equation that comes with a specific condition, called the initial condition. This condition helps us find a unique solution for the differential equation. In our case, we have the differential equation \(y'(t) = \frac{2t^2 + 4}{t}\) with the initial condition \(y(1) = 2\). The initial condition acts like a starting point, fixing one point of the function at \(t = 1\). Without it, we could have infinitely many solutions all differing by a constant. When we solve the differential equation, this initial condition allows us to pinpoint the exact path the function must take. It's like setting the story for how a curve behaves on a graph.
Integration
Integration is a mathematical process used to find a function from its derivative, essentially "undoing" differentiation. When we integrate a function, we are looking for the original function that, when differentiated, gives us the integrand (the function inside the integral sign).In the problem, we want to find \(y(t)\) using \(y'(t)\). For this, we need to perform integration: \[ \int y'(t) \, dt = \int \frac{2t^2 + 4}{t} \, dt \] After simplifying, this becomes: \[ \int (2t + \frac{4}{t}) \, dt \] We decompose the integral into two simpler parts to make the integration more manageable: - \(\int 2t \, dt\) - \(\int \frac{4}{t} \, dt\)Each of these can be integrated separately, giving us a step towards finding \(y(t)\).
Antiderivatives
Antiderivatives, also known as indefinite integrals, are functions that reverse the process of differentiation. If \(F(t)\) is an antiderivative of \(f(t)\), then \(F'(t) = f(t)\). The notation for finding an antiderivative is \[ F(t) = \int f(t) \, dt + C \] where \(C\) is the constant of integration. In our exercise, we compute the antiderivatives for the parts of our integral: - \( \int 2t \, dt = t^2 + C_1 \) - \( \int \frac{4}{t} \, dt = 4\ln|t| + C_2 \)Combining these gives us \(y(t) = t^2 + 4\ln|t| + C\). The constant \(C\) encapsulates any constant terms from integration, which will be determined using our initial condition later.
Natural Logarithm
The natural logarithm, denoted as \(\ln(x)\), is a logarithm with the base \(e\), where \(e\) is an irrational constant approximately equal to 2.71828. It's a crucial function in calculus because it arises often when dealing with growth and time-based processes. In our exercise, we encounter the integral \(\int \frac{4}{t} \, dt\), which results in the natural logarithm: \[ \int \frac{4}{t} \, dt = 4 \ln|t| + C \] This step is integral for understanding how magnitudes scale multiplicatively. Unlike regular logarithms, \(\ln(x)\) directly relates to the exponential function, making it exceedingly useful for calculus operations that involve exponential growth. In this problem, it appears in the expression for \(y(t)\), showcasing its common appearance in differential equations solutions.

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Most popular questions from this chapter

A differential equation of the form \(y^{\prime}(t)=F(y)\) is said to be autonomous (the function \(F\) depends only on \(y\) ). The constant function \(y=y_{0}\) is an equilibrium solution of the equation provided \(F\left(y_{0}\right)=0\) (because then \(y^{\prime}(t)=0,\) and the solution remains constant for all \(t\) ). Note that equilibrium solutions correspond to horizontal line segments in the direction field. Note also that for autonomous equations, the direction field is independent of \(t\). Consider the following equations. a. Find all equilibrium solutions. b. Sketch the direction field on either side of the equilibrium solutions for \(t \geq 0\). c. Sketch the solution curve that corresponds to the initial condition \(y(0)=1\). $$y^{\prime}(t)=y(2-y)$$

Compute \(\int_{0}^{1} \ln x d x\) using integration by parts. Then explain why \(-\int_{0}^{\infty} e^{-x} d x\) (an easier integral) gives the same result.

Recall that the substitution \(x=a \sec \theta\) implies either \(x \geq a\) (in which case \(0 \leq \theta<\pi / 2\) and \(\tan \theta \geq 0)\) or \(x \leq-a\) (in which case \(\pi / 2<\theta \leq \pi\) and \(\tan \theta \leq 0\) ). Graph the function \(f(x)=\frac{\sqrt{x^{2}-9}}{x}\) and consider the region bounded by the curve and the \(x\) -axis on \([-6,-3] .\) Then evaluate \(\int_{-6}^{-3} \frac{\sqrt{x^{2}-9}}{x} d x .\) Be sure the result is consistent with the graph.

Approximate the following integrals using Simpson's Rule. Experiment with values of \(n\) to ensure that the error is less than \(10^{-3}\). \(\int_{0}^{\pi} \frac{4 \cos x}{5-4 \cos x} d x=\frac{2 \pi}{3}\)

Apply Simpson's Rule to the following integrals. It is easiest to obtain the Simpson's Rule approximations from the Trapezoid Rule approximations, as in Example \(7 .\) Make \(a\) table similar to Table 7.8 showing the approximations and errors for \(n=4,8,16,\) and \(32 .\) The exact values of the integrals are given for computing the error. \(\int_{0}^{4}\left(3 x^{5}-8 x^{3}\right) d x=1536\)

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