1. **State the problem:** Express the rational function $$\frac{5x^2 + 2}{2x^2 + x}$$ as a sum of partial fractions.
2. **Factor the denominator:**
$$2x^2 + x = x(2x + 1)$$
3. **Set up the partial fractions:**
Since the denominator factors into linear terms, we write:
$$\frac{5x^2 + 2}{x(2x + 1)} = \frac{A}{x} + \frac{B}{2x + 1}$$
4. **Multiply both sides by the denominator to clear fractions:**
$$5x^2 + 2 = A(2x + 1) + Bx$$
5. **Expand the right side:**
$$5x^2 + 2 = 2Ax + A + Bx = (2A + B)x + A$$
6. **Equate coefficients of like powers of $x$:**
- Coefficient of $x^2$: Left side has 5, right side has 0, so $5 = 0$ (contradiction)
This indicates the degree of numerator is not less than denominator, so we must perform polynomial division first.
7. **Perform polynomial division:**
Divide $5x^2 + 2$ by $2x^2 + x$:
$$\frac{5x^2 + 2}{2x^2 + x} = Q(x) + \frac{R(x)}{2x^2 + x}$$
Divide leading terms:
$$\frac{5x^2}{2x^2} = \frac{5}{2}$$
Multiply divisor by $\frac{5}{2}$:
$$\frac{5}{2}(2x^2 + x) = 5x^2 + \frac{5}{2}x$$
Subtract:
$$\left(5x^2 + 2\right) - \left(5x^2 + \frac{5}{2}x\right) = -\frac{5}{2}x + 2$$
So:
$$\frac{5x^2 + 2}{2x^2 + x} = \frac{5}{2} + \frac{-\frac{5}{2}x + 2}{2x^2 + x}$$
8. **Express the remainder fraction as partial fractions:**
$$\frac{-\frac{5}{2}x + 2}{x(2x + 1)} = \frac{A}{x} + \frac{B}{2x + 1}$$
Multiply both sides by denominator:
$$-\frac{5}{2}x + 2 = A(2x + 1) + Bx = (2A + B)x + A$$
Equate coefficients:
- Coefficient of $x$: $-\frac{5}{2} = 2A + B$
- Constant term: $2 = A$
9. **Solve for $A$ and $B$:**
From constant term:
$$A = 2$$
Substitute into $x$ coefficient:
$$-\frac{5}{2} = 2(2) + B = 4 + B$$
$$B = -\frac{5}{2} - 4 = -\frac{5}{2} - \frac{8}{2} = -\frac{13}{2}$$
10. **Write the final partial fraction decomposition:**
$$\frac{5x^2 + 2}{2x^2 + x} = \frac{5}{2} + \frac{2}{x} - \frac{13}{2(2x + 1)}$$
**Answer:**
$$\boxed{\frac{5x^2 + 2}{2x^2 + x} = \frac{5}{2} + \frac{2}{x} - \frac{13}{2(2x + 1)}}$$
Partial Fractions F9Bfa8
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