MHB Dividing vs Subtracting to Solve Equations w/1 Variable

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SUMMARY

The discussion centers on solving the differential equation \(\frac{dx}{dt}=4(x^2+1)\). Participants emphasize that dividing both sides by \(4(x^2+1)\) is the correct method, as it allows for the separation of variables without risking division by zero. Subtracting \(4(x^2+1)\) from both sides leads to an incorrect formulation, resulting in a different answer upon integration. The consensus is that division is the mathematically sound approach for this separable equation.

PREREQUISITES
  • Understanding of differential equations
  • Familiarity with the concept of separable equations
  • Knowledge of integration techniques
  • Basic algebraic manipulation skills
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  • Study the method of separation of variables in differential equations
  • Learn about integrating factors for non-separable equations
  • Explore the implications of division by zero in mathematical equations
  • Practice solving various separable differential equations
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Students and educators in mathematics, particularly those focusing on differential equations, as well as anyone looking to enhance their problem-solving skills in calculus.

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If you have the equation [math]\frac{dx}{dt}=4(x^2+1)[/math] I sometimes get confused if i should should subtract [math]4(x^2+1)[/math] from both sides or multiply by it's reciprocal. If I subtract from both sides then I'd have 0 on the right side and that would give a different answer after integration but mathematically why would it be wrong?
 
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Re: Dividing vs subtracting to get all terms with one variable to one side of equation

find_the_fun said:
If you have the equation [math]\frac{dx}{dt}=4(x^2+1)[/math] I sometimes get confused if i should should subtract [math]4(x^2+1)[/math] from both sides or multiply by it's reciprocal. If I subtract from both sides then I'd have 0 on the right side and that would give a different answer after integration but mathematically why would it be wrong?

Since for all real x is $ 4\ (x^{2} + 1) > 0$ You can divide both sides by $ 4\ (x^{2} + 1)$ without danger and then integrate separately in x and y...

Kind regards

$\chi$ $\sigma$
 
Re: Dividing vs subtracting to get all terms with one variable to one side of equation

find_the_fun said:
If you have the equation [math]\frac{dx}{dt}=4(x^2+1)[/math] I sometimes get confused if i should should subtract [math]4(x^2+1)[/math] from both sides or multiply by it's reciprocal. If I subtract from both sides then I'd have 0 on the right side and that would give a different answer after integration but mathematically why would it be wrong?

Since this equation is separable, the best approach would be to divide so that you can separate variables, and as chisigma pointed out, you can do this without worrying about division by zero, and thus you are eliminating no solutions.
 

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