👉 Try now NerdPal! Our new math app on iOS and Android

Find the integral $\int\frac{4x-1}{x^3-2x^2-x}dx$

Step-by-step Solution

Go!
Math mode
Text mode
Go!
1
2
3
4
5
6
7
8
9
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

Final Answer

$\ln\left(x\right)+\ln\left(\frac{\sqrt{2}}{\sqrt{-2+\left(x-1\right)^2}}\right)+\frac{5\sqrt{2}}{4}\ln\left(-2.414214+x\right)-\frac{5\sqrt{2}}{4}\ln\left(0.414214+x\right)+C_0$
Got another answer? Verify it here!

Step-by-step Solution

Specify the solving method

1

Rewrite the expression $\frac{4x-1}{x^3-2x^2-x}$ inside the integral in factored form

$\int\frac{4x-1}{x\left(x^2-2x-1\right)}dx$
2

Rewrite the fraction $\frac{4x-1}{x\left(x^2-2x-1\right)}$ in $2$ simpler fractions using partial fraction decomposition

$\frac{4x-1}{x\left(x^2-2x-1\right)}=\frac{A}{x}+\frac{Bx+C}{x^2-2x-1}$
3

Find the values for the unknown coefficients: $A, B, C$. The first step is to multiply both sides of the equation from the previous step by $x\left(x^2-2x-1\right)$

$4x-1=x\left(x^2-2x-1\right)\left(\frac{A}{x}+\frac{Bx+C}{x^2-2x-1}\right)$
4

Multiplying polynomials

$4x-1=\frac{x\left(x^2-2x-1\right)A}{x}+\frac{x\left(x^2-2x-1\right)\left(Bx+C\right)}{x^2-2x-1}$
5

Simplifying

$4x-1=\left(x^2-2x-1\right)A+x\left(Bx+C\right)$
6

Assigning values to $x$ we obtain the following system of equations

$\begin{matrix}-1=-A&\:\:\:\:\:\:\:(x=0) \\ 3=-2A+B+C&\:\:\:\:\:\:\:(x=1) \\ -5=2A+B-C&\:\:\:\:\:\:\:(x=-1)\end{matrix}$
7

Proceed to solve the system of linear equations

$\begin{matrix} -1A & + & 0B & + & 0C & =-1 \\ -2A & + & 1B & + & 1C & =3 \\ 2A & + & 1B & - & 1C & =-5\end{matrix}$
8

Rewrite as a coefficient matrix

$\left(\begin{matrix}-1 & 0 & 0 & -1 \\ -2 & 1 & 1 & 3 \\ 2 & 1 & -1 & -5\end{matrix}\right)$
9

Reducing the original matrix to a identity matrix using Gaussian Elimination

$\left(\begin{matrix}1 & 0 & 0 & 1 \\ 0 & 1 & 0 & -1 \\ 0 & 0 & 1 & 6\end{matrix}\right)$
10

The integral of $\frac{4x-1}{x\left(x^2-2x-1\right)}$ in decomposed fraction equals

$\int\left(\frac{1}{x}+\frac{-x+6}{x^2-2x-1}\right)dx$
11

Expand the integral $\int\left(\frac{1}{x}+\frac{-x+6}{x^2-2x-1}\right)dx$ into $2$ integrals using the sum rule for integrals, to then solve each integral separately

$\int\frac{1}{x}dx+\int\frac{-x+6}{x^2-2x-1}dx$
12

The integral $\int\frac{1}{x}dx$ results in: $\ln\left(x\right)$

$\ln\left(x\right)$
13

Gather the results of all integrals

$\ln\left(x\right)+\int\frac{-x+6}{x^2-2x-1}dx$
14

Rewrite the expression $\frac{-x+6}{x^2-2x-1}$ inside the integral in factored form

$\ln\left(x\right)+\int\frac{-x+6}{-2+\left(x-1\right)^2}dx$
15

The integral $\int\frac{-x+6}{-2+\left(x-1\right)^2}dx$ results in: $-\frac{5\sqrt{2}}{4}\ln\left(0.414214+x\right)+\frac{5\sqrt{2}}{4}\ln\left(-2.414214+x\right)+\ln\left(\frac{\sqrt{2}}{\sqrt{-2+\left(x-1\right)^2}}\right)$

$-\frac{5\sqrt{2}}{4}\ln\left(0.414214+x\right)+\frac{5\sqrt{2}}{4}\ln\left(-2.414214+x\right)+\ln\left(\frac{\sqrt{2}}{\sqrt{-2+\left(x-1\right)^2}}\right)$
16

Gather the results of all integrals

$\ln\left(x\right)+\ln\left(\frac{\sqrt{2}}{\sqrt{-2+\left(x-1\right)^2}}\right)+\frac{5\sqrt{2}}{4}\ln\left(-2.414214+x\right)-\frac{5\sqrt{2}}{4}\ln\left(0.414214+x\right)$
17

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

$\ln\left(x\right)+\ln\left(\frac{\sqrt{2}}{\sqrt{-2+\left(x-1\right)^2}}\right)+\frac{5\sqrt{2}}{4}\ln\left(-2.414214+x\right)-\frac{5\sqrt{2}}{4}\ln\left(0.414214+x\right)+C_0$

Final Answer

$\ln\left(x\right)+\ln\left(\frac{\sqrt{2}}{\sqrt{-2+\left(x-1\right)^2}}\right)+\frac{5\sqrt{2}}{4}\ln\left(-2.414214+x\right)-\frac{5\sqrt{2}}{4}\ln\left(0.414214+x\right)+C_0$

Explore different ways to solve this problem

Give us your feedback!

Function Plot

Plotting: $\ln\left(x\right)+\ln\left(\frac{\sqrt{2}}{\sqrt{-2+\left(x-1\right)^2}}\right)+\frac{5\sqrt{2}}{4}\ln\left(-2.414214+x\right)-\frac{5\sqrt{2}}{4}\ln\left(0.414214+x\right)+C_0$

SnapXam A2
Answer Assistant

beta
Got a different answer? Verify it!

Go!
1
2
3
4
5
6
7
8
9
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

How to improve your answer:

Main Topic: Integrals by Partial Fraction Expansion

The partial fraction decomposition or partial fraction expansion of a rational function is the operation that consists in expressing the fraction as a sum of a polynomial (possibly zero) and one or several fractions with a simpler denominator.

Used Formulas

7. See formulas

Your Math & Physics Tutor. Powered by AI

Available 24/7, 365.

Unlimited step-by-step math solutions. No ads.

Includes multiple solving methods.

Support for more than 100 math topics.

Premium access on our iOS and Android apps as well.

20% discount on online tutoring.

Choose your subscription plan:
Have a promo code?
Pay $39.97 USD securely with your payment method.
Please hold while your payment is being processed.
Create an Account