Solve the differential equation $\frac{dy}{dx}=y\left(1-y\right)$

Step-by-step Solution

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Final answer to the problem

$y=\frac{e^x}{C_1+e^x}$
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Step-by-step Solution

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  • Exact Differential Equation
  • Linear Differential Equation
  • Separable Differential Equation
  • Homogeneous Differential Equation
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  • Product of Binomials with Common Term
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1

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

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

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

$\int\frac{1}{y\left(1-y\right)}dy=\int1dx$

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

$\frac{1}{y}+\frac{1}{1-y}$

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

$\int\frac{1}{y}dy+\int\frac{1}{1-y}dy$

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

$\ln\left|y\right|+\int\frac{1}{1-y}dy$

Apply the formula: $\int\frac{n}{ax+b}dx$$=\frac{n}{a}\ln\left(ax+b\right)+C$, where $a=-1$, $b=1$, $x=y$ and $n=1$

$\ln\left|y\right|+\frac{1}{-1}\ln\left|-y+1\right|$

Divide $1$ by $-1$

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

Solve the integral $\int\frac{1}{y\left(1-y\right)}dy$ and replace the result in the differential equation

$\ln\left|y\right|-\ln\left|-y+1\right|=\int1dx$

The integral of a constant is equal to the constant times the integral's variable

$x$

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

$x+C_0$
4

Solve the integral $\int1dx$ and replace the result in the differential equation

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

The difference of two logarithms of equal base $b$ is equal to the logarithm of the quotient: $\log_b(x)-\log_b(y)=\log_b\left(\frac{x}{y}\right)$

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

Take the variable outside of the logarithm

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

Simplifying the logarithm

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

Simplify $e^{\left(x+C_0\right)}$ applying properties of exponents

$\frac{y}{-y+1}=C_1e^x$

Take the reciprocal of both sides of the equation

$\frac{-y+1}{y}=\frac{1}{C_1e^x}$

We can rename $\frac{1}{C_1e^x}$ as other constant

$\frac{-y+1}{y}=\frac{C_1}{e^x}$

Simplify the fraction $\frac{-y+1}{y}$

$-1+\frac{1}{y}=\frac{C_1}{e^x}$

Group the terms of the equation

$\frac{1}{y}=\frac{C_1}{e^x}+1$

Take the reciprocal of both sides of the equation

$y=\frac{1}{\frac{C_1}{e^x}+1}$

Combine $\frac{C_1}{e^x}+1$ in a single fraction

$y=\frac{1}{\frac{C_1+e^x}{e^x}}$

Divide fractions $\frac{1}{\frac{C_1+e^x}{e^x}}$ with Keep, Change, Flip: $a\div \frac{b}{c}=\frac{a}{1}\div\frac{b}{c}=\frac{a}{1}\times\frac{c}{b}=\frac{a\cdot c}{b}$

$y=\frac{e^x}{C_1+e^x}$
5

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

$y=\frac{e^x}{C_1+e^x}$

Final answer to the problem

$y=\frac{e^x}{C_1+e^x}$

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Function Plot

Plotting: $\frac{dy}{dx}-y\left(1-y\right)$

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7
8
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0
a
b
c
d
f
g
m
n
u
v
w
x
y
z
.
(◻)
+
-
×
◻/◻
/
÷
2

e
π
ln
log
log
lim
d/dx
Dx
|◻|
θ
=
>
<
>=
<=
sin
cos
tan
cot
sec
csc

asin
acos
atan
acot
asec
acsc

sinh
cosh
tanh
coth
sech
csch

asinh
acosh
atanh
acoth
asech
acsch

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