1. Recognise that the fraction is improper and perform long division to extract the polynomial part.
The degree of the numerator (2x3−5) is 3, and the degree of the denominator (x3−x2) is also 3. Thus, the fraction is improper.
x3−x22x3−5=2+x2(x−1)2x2−5
2. Set up the partial fraction decomposition for the proper fraction part.
Let x2(x−1)2x2−5=xA+x2B+x−1C
Multiplying throughout by x2(x−1):
2x2−5=Ax(x−1)+B(x−1)+Cx2
3. Solve for the constants $B$ and $C$ by substituting suitable values of $x$.
Substitute x=0:
2(0)2−5=A(0)(−1)+B(−1)+C(0)2
−5=−B⟹B=5
Substitute x=1:
2(1)2−5=A(1)(0)+B(0)+C(1)2
−3=C⟹C=−3
4. Solve for the constant $A$ by comparing coefficients.
Compare the coefficients of x2 on both sides:
2=A+C
Since C=−3:
2=A−3⟹A=5
5. Write the final expression in partial fractions.
x2(x−1)2x3−5=2+x5+x25−x−13
答案2+x5+x25−x−13