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Separable Differential Equations Calculator

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1

Here, we show you a step-by-step solved example of separable differential equations. This solution was automatically generated by our smart calculator:

$\left(2xy-y\right)dx+\left(x^2+x\right)dy=0$
2

Factoring by $y$

$y\left(2x-1\right)dx+\left(x^2+x\right)dy=0$
3

Grouping the terms of the differential equation

$\left(x^2+x\right)dy=-\left(2x-1\right)y\cdot dx$
4

Group the terms of the differential equation. Move the terms of the $y$ variable to the left side, and the terms of the $x$ variable to the right side of the equality

$\frac{1}{y}dy=\frac{-\left(2x-1\right)}{x^2+x}dx$

Factor the polynomial $x^2+x$ by it's greatest common factor (GCF): $x$

$\frac{-\left(2x-1\right)}{x\left(x+1\right)}dx$
5

Simplify the expression $\frac{-\left(2x-1\right)}{x^2+x}dx$

$\frac{1}{y}dy=\frac{-\left(2x-1\right)}{x\left(x+1\right)}dx$
6

Integrate both sides of the differential equation, the left side with respect to $y$, and the right side with respect to $x$

$\int\frac{1}{y}dy=\int\frac{-\left(2x-1\right)}{x\left(x+1\right)}dx$

The integral of the inverse of the lineal function is given by the following formula, $\displaystyle\int\frac{1}{x}dx=\ln(x)$

$\ln\left|y\right|$
7

Solve the integral $\int\frac{1}{y}dy$ and replace the result in the differential equation

$\ln\left|y\right|=\int\frac{-\left(2x-1\right)}{x\left(x+1\right)}dx$

Take out the constant $-1$ from the integral

$-\int\frac{2x-1}{x\left(x+1\right)}dx$

Rewrite the fraction $\frac{2x-1}{x\left(x+1\right)}$ in $2$ simpler fractions using partial fraction decomposition

$\frac{-1}{x}+\frac{3}{x+1}$

Expand the integral $\int\left(\frac{-1}{x}+\frac{3}{x+1}\right)dx$ into $2$ integrals using the sum rule for integrals, to then solve each integral separately

$-\int\frac{-1}{x}dx-\int\frac{3}{x+1}dx$

We can solve the integral $\int\frac{3}{x+1}dx$ by applying integration by substitution method (also called U-Substitution). First, we must identify a section within the integral with a new variable (let's call it $u$), which when substituted makes the integral easier. We see that $x+1$ it's a good candidate for substitution. Let's define a variable $u$ and assign it to the choosen part

$u=x+1$

Now, in order to rewrite $dx$ in terms of $du$, we need to find the derivative of $u$. We need to calculate $du$, we can do that by finding the derivative of the equation above

$du=dx$

Substituting $u$ and $dx$ in the integral and simplify

$-\int\frac{-1}{x}dx-\int\frac{3}{u}du$

The integral of the inverse of the lineal function is given by the following formula, $\displaystyle\int\frac{1}{x}dx=\ln(x)$

$- -\ln\left|x\right|-\int\frac{3}{u}du$

Multiply $-1$ times $-1$

$\ln\left|x\right|-\int\frac{3}{u}du$

The integral of the inverse of the lineal function is given by the following formula, $\displaystyle\int\frac{1}{x}dx=\ln(x)$

$\ln\left|x\right|- 3\ln\left|u\right|$

Multiply $-1$ times $3$

$\ln\left|x\right|-3\ln\left|u\right|$

Replace $u$ with the value that we assigned to it in the beginning: $x+1$

$\ln\left|x\right|-3\ln\left|x+1\right|$

As the integral that we are solving is an indefinite integral, when we finish integrating we must add the constant of integration $C$

$\ln\left|x\right|-3\ln\left|x+1\right|+C_0$
8

Solve the integral $\int\frac{-\left(2x-1\right)}{x\left(x+1\right)}dx$ and replace the result in the differential equation

$\ln\left|y\right|=\ln\left|x\right|-3\ln\left|x+1\right|+C_0$

Take the variable outside of the logarithm

$e^{\ln\left(y\right)}=e^{\left(\ln\left(x\right)-3\ln\left(x+1\right)+C_0\right)}$

Simplifying the logarithm

$y=e^{\left(\ln\left(x\right)-3\ln\left(x+1\right)+C_0\right)}$

Simplify $e^{\left(\ln\left(x\right)-3\ln\left(x+1\right)+C_0\right)}$ by applying the properties of exponents and logarithms

$y=xe^{\left(-3\ln\left(x+1\right)+C_0\right)}$

Simplify $e^{\left(-3\ln\left(x+1\right)+C_0\right)}$ by applying the properties of exponents and logarithms

$y=e^{C_0}x\left(x+1\right)^{-3}$

We can rename $e^{C_0}$ as other constant

$y=C_1x\left(x+1\right)^{-3}$

Applying the property of exponents, $\displaystyle a^{-n}=\frac{1}{a^n}$, where $n$ is a number

$y=C_1x\frac{1}{\left(x+1\right)^{3}}$

Multiply the fraction by the term

$y=\frac{C_1x}{\left(x+1\right)^{3}}$
9

Find the explicit solution to the differential equation. We need to isolate the variable $y$

$y=\frac{C_1x}{\left(x+1\right)^{3}}$

Final answer to the exercise

$y=\frac{C_1x}{\left(x+1\right)^{3}}$

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