How do you integrate 10/(5x^2-2x^3)105x22x3 using partial fractions?

1 Answer
Feb 2, 2017

The answer is =-2/x+4/5ln(|x|)-4/5ln(|2x-5|)+C=2x+45ln(|x|)45ln(|2x5|)+C

Explanation:

5x^2-2x^3=-x^2(2x-5)5x22x3=x2(2x5)

Let's perform the decompostion into partial fractions

10/(5x^2-2x^3)=-10/((x^2(2x-5)))105x22x3=10(x2(2x5))

=A/x^2+B/x+C/(2x-5)=Ax2+Bx+C2x5

=(A(2x-5)+Bx(2x-5)+Cx^2)/((x^2(2x-5)))=A(2x5)+Bx(2x5)+Cx2(x2(2x5))

The denpminators are the same, we can compare the numerators

-10=A(2x-5)+Bx(2x-5)+Cx^210=A(2x5)+Bx(2x5)+Cx2

Let x=0x=0, =>, -10=-5A10=5A, =>, A=2A=2

Let x=5/2x=52, =>, -10=25/4C10=254C, =>, C=-8/5C=85

Coefficients of x^2x2

0=2B+C0=2B+C, =>, B=-C/2=1/2*8/5=4/5B=C2=1285=45

Therefore,

10/(5x^2-2x^3)=2/x^2+(4/5)/x+(-8/5)/(2x-5)105x22x3=2x2+45x+852x5

So,

int(10dx)/(5x^2-2x^3)=2intdx/x^2+4/5intdx/x-8/5intdx/(2x-5)10dx5x22x3=2dxx2+45dxx85dx2x5

=-2/x+4/5ln(|x|)-4/5ln(|2x-5|)+C=2x+45ln(|x|)45ln(|2x5|)+C