Find the solution to the differential equation

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SUMMARY

The discussion focuses on solving the differential equation dx/dt = (x² - 1) / t with the initial condition x(1) = 2. The user successfully separated the variables but struggled with integrating the left-hand side (LHS), specifically ∫(1/(x² - 1)) dx. It was confirmed that the correct solution is x = (t² + 3)/(3 - t²), as stated in the answer book. The integration method required is partial fractions, and the user was advised to rearrange the equation to express t as a function of x.

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Yaaaldi
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Homework Statement



Find the solution when x(1)=2
dx/dt = (x2 - 1) / t






The Attempt at a Solution




I got all the variables to separate sides:

1/(x2 - 1) dx = 1/t dt

However I don't know how to integrate the LHS to get the correct answer.

The answer book says:

x = (t2 + 3)/(3 - t2)

Is the answer in the book wrong? I don't know how to integrate 1/(x2 - 1) without using the trig identity which isn't in the answers..
 
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Do you know the method of integration by partial fractions? That is what you'll need for \int \frac{1}{x^{2} - 1 } dx. (You could also use a trig substitution, but that's a bit excessive here...)

You will also need to do some algebra because integrating your separated differential equation is going to give you t(x) , rather than x(t) .

EDIT: Came back to this to finish working it through. The book's answer is correct.
 
Last edited:

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