Math Problem Statement

Given \( \frac{2 + 5x - x^2}{x^2(x + 1)} = \frac{A}{x} + \frac{B}{x^2} + \frac{C}{x + 1} \), find values for A, B, and C.

Solution

The given equation is:

2+5xx2x2(x+1)=Ax+Bx2+Cx+1\frac{2 + 5x - x^2}{x^2(x + 1)} = \frac{A}{x} + \frac{B}{x^2} + \frac{C}{x + 1}

We are tasked with determining the values of AA, BB, and CC by performing partial fraction decomposition.

Step 1: Express the equation in terms of a single denominator.

The right-hand side of the equation needs to be combined into a single fraction with the denominator x2(x+1)x^2(x + 1). Start by adding the fractions:

Ax+Bx2+Cx+1\frac{A}{x} + \frac{B}{x^2} + \frac{C}{x+1}

The least common denominator is x2(x+1)x^2(x + 1). Rewrite each term with this common denominator:

Ax=A(x+1)x2(x+1),Bx2=B(x+1)x2(x+1),Cx+1=Cx2x2(x+1)\frac{A}{x} = \frac{A(x + 1)}{x^2(x + 1)}, \quad \frac{B}{x^2} = \frac{B(x + 1)}{x^2(x + 1)}, \quad \frac{C}{x + 1} = \frac{C x^2}{x^2(x + 1)}

Thus, the right-hand side becomes:

A(x+1)+B(x+1)+Cx2x2(x+1)\frac{A(x + 1) + B(x + 1) + Cx^2}{x^2(x + 1)}

Step 2: Set up the equation.

Now, set the numerators equal to each other:

2+5xx2=A(x+1)+B(x+1)+Cx22 + 5x - x^2 = A(x + 1) + B(x + 1) + Cx^2

Step 3: Expand and collect like terms.

Expand both sides:

2+5xx2=A(x+1)+B(x+1)+Cx22 + 5x - x^2 = A(x + 1) + B(x + 1) + Cx^2

2+5xx2=(A+B)(x+1)+Cx22 + 5x - x^2 = (A + B)(x + 1) + Cx^2

2+5xx2=(A+B)x+(A+B)+Cx22 + 5x - x^2 = (A + B)x + (A + B) + Cx^2

Now group terms:

2+5xx2=Cx2+(A+B)x+(A+B)2 + 5x - x^2 = Cx^2 + (A + B)x + (A + B)

Step 4: Equate the coefficients.

By comparing the coefficients of x2x^2, xx, and the constant terms, we get the following system of equations:

  1. Coefficient of x2x^2: 1=C-1 = C
  2. Coefficient of xx: 5=A+B5 = A + B
  3. Constant term: 2=A+B2 = A + B

Step 5: Solve the system of equations.

From equation (1), we know C=1C = -1.

Now substitute A+B=5A + B = 5 into the constant equation A+B=2A + B = 2. We can subtract these two equations:

(5)(2)=A+B(A+B)(5) - (2) = A + B - (A + B) 0=00 = 0

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Math Problem Analysis

Mathematical Concepts

Partial Fraction Decomposition
Algebra

Formulas

\frac{P(x)}{Q(x)} = \frac{A}{x} + \frac{B}{x^2} + \frac{C}{x + 1}

Theorems

Partial Fraction Decomposition

Suitable Grade Level

Grades 10-12