Initial value problem, end of problem Q

In summary: Just remember to account for the + C in the end. In summary, the conversation is about solving an initial value problem using the equation x2(dy/dx) = (4x2-x-2)/((x+1)(y+1)), with the initial condition y(1)=1. The person has solved the equation and found y2/2 + y = log(x) + 2/x + 3log(x+1) + C, but is unsure if it can be solved further. Another person suggests setting it up as a quadratic and using the quadratic formula to find values of y. The first person then asks if they can just complete the square instead, and the second person confirms that it should work, but
  • #1
csc2iffy
76
0

Homework Statement


Solve the I.V.P. x2(dy/dx) = (4x2-x-2)/((x+1)(y+1)) , y(1)=1


Homework Equations





The Attempt at a Solution


So far, I got to this:
y2/2 + y = log(x) + 2/x + 3log(x+1) + C
I used the initial conditions to solve for C and got:
C = -1/2 - 3log(2)
Substituting C back in:
y2/2 + y = log(x) + 2/x + 3log(x+1) + (-1/2 - 3log(2))
Now my question is, is it possible to solve for y or is this as far as I can go with the problem?
 
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  • #2
csc2iffy said:
y2/2 + y = log(x) + 2/x + 3log(x+1) + (-1/2 - 3log(2))
Now my question is, is it possible to solve for y or is this as far as I can go with the problem?

Well it is a quadratic, not the nicest one but you can solve it for y.
 
  • #3
How do I set it up as a quadratic? I'm getting a little lost with all of the variables
 
  • #4
csc2iffy said:
How do I set it up as a quadratic? I'm getting a little lost with all of the variables

[tex]y^2 + 2y -2[\frac{2}{x} + \ln(x(x+1)^3)] = 0[/tex]

[tex]\text{Then quadratic formula } y = \frac{-2\pm\sqrt{4 - 4(1)(-2[\frac{2}{x} + \ln(x(x+1)^3)])}}{2(1)}[/tex]

It's horrible, but it'll give you values of y.
 
Last edited:
  • #5
could i just complete the square to get:
y = +/- √[2(log(x) + (2/x) + 3log(x+1) + C) + 1] - 1
?
 
  • #6
Bread18 said:
[tex]y^2 + 2y -2[\frac{2}{x} + \ln(x(x+1)^3)] = 0[/tex]

[tex]\text{Then quadratic formula } y = \frac{-2\pm\sqrt{4 - 4(1)(-2[\frac{2}{x} + \ln(x(x+1)^3)])}}{2(1)}[/tex]

It's horrible, but it'll give you values of y.

Oops forgot the + C, but you get the idea.

csc2iffy said:
could i just complete the square to get:
y = +/- √[2(log(x) + (2/x) + 3log(x+1) + C) + 1] - 1
?

Completing the square would probably be a lot harder, but it should work.
 

1. What is an initial value problem (IVP)?

An initial value problem is a type of differential equation that involves finding a solution for a function based on an initial condition. This means that the solution must satisfy both the differential equation and an initial condition, typically given in the form of a specific value for the function at a certain point.

2. What is the significance of solving an IVP?

Solving an initial value problem is important in many fields of science and engineering, as it allows us to model and predict the behavior of systems over time. It is also a fundamental concept in calculus and differential equations, and is used in a variety of mathematical applications.

3. How do you solve an initial value problem?

The process of solving an initial value problem involves finding a general solution to the differential equation, and then using the initial condition to determine the specific solution that satisfies both the equation and the given condition. This can be done using various methods, such as separation of variables, substitution, or using an integrating factor.

4. What is the difference between an initial value problem and a boundary value problem?

The main difference between an initial value problem and a boundary value problem is that an IVP involves finding a solution that satisfies an initial condition, while a boundary value problem involves finding a solution that satisfies conditions at different points (usually the boundaries) of the domain of the function. Additionally, the methods used to solve these types of problems may differ.

5. Can all initial value problems be solved analytically?

No, not all initial value problems can be solved analytically. In some cases, the differential equation may not have a closed-form solution, or the solution may be too complex to find using traditional methods. In these cases, numerical methods or approximations may be used to find an approximate solution.

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