Accedmychevron_right11thchevron_rightmathchevron_rightPartial Fractionschevron_rightExercise 5.1

Solution

Factor:

(x21)2=(x1)2(x+1)2(x^2-1)^2=(x-1)^2(x+1)^2

Let:

x2+x(x1)2(x+1)2=Ax1+B(x1)2+Cx+1+D(x+1)2\frac{x^2+x}{(x-1)^2(x+1)^2}=\frac{A}{x-1}+\frac{B}{(x-1)^2}+\frac{C}{x+1}+\frac{D}{(x+1)^2}

Solving gives:

A=14,B=12,C=14,D=0A=\frac14,\quad B=\frac12,\quad C=-\frac14,\quad D=0

Hence:

x2+x(x21)2=14(x1)+12(x1)214(x+1)\boxed{\frac{x^2+x}{(x^2-1)^2}=\frac{1}{4(x-1)}+\frac{1}{2(x-1)^2}-\frac{1}{4(x+1)}}