1. **State the problem:**
Divide the polynomial $4x^3 - 4x^2 - 16x + 7$ by the product $(x+1)(x-2)$ using long division, then express the result as partial fractions.
2. **Rewrite the divisor:**
Note that $(x+1)(x-2) = x^2 - x - 2$.
3. **Perform long division:**
Divide $4x^3 - 4x^2 - 16x + 7$ by $x^2 - x - 2$.
- First term: $\frac{4x^3}{x^2} = 4x$.
- Multiply divisor by $4x$: $4x(x^2 - x - 2) = 4x^3 - 4x^2 - 8x$.
- Subtract:
$$\left(4x^3 - 4x^2 - 16x + 7\right) - \left(4x^3 - 4x^2 - 8x\right) = -8x + 7$$
4. **Express remainder over divisor:**
The division gives quotient $4x$ and remainder $-8x + 7$.
So,
$$\frac{4x^3 - 4x^2 - 16x + 7}{(x+1)(x-2)} = 4x + \frac{-8x + 7}{(x+1)(x-2)}$$
5. **Express the remainder fraction in partial fractions:**
Assume
$$\frac{-8x + 7}{(x+1)(x-2)} = \frac{A}{x+1} + \frac{B}{x-2}$$
Multiply both sides by $(x+1)(x-2)$:
$$-8x + 7 = A(x-2) + B(x+1)$$
6. **Find coefficients A and B:**
Set $x = 2$:
$$-8(2) + 7 = A(0) + B(3) \Rightarrow -16 + 7 = 3B \Rightarrow -9 = 3B \Rightarrow B = -3$$
Set $x = -1$:
$$-8(-1) + 7 = A(-3) + B(0) \Rightarrow 8 + 7 = -3A \Rightarrow 15 = -3A \Rightarrow A = -5$$
7. **Write the final partial fraction decomposition:**
$$\frac{4x^3 - 4x^2 - 16x + 7}{(x+1)(x-2)} = 4x - \frac{5}{x+1} - \frac{3}{x-2}$$
**Final answer:**
$$\boxed{4x - \frac{5}{x+1} - \frac{3}{x-2}}$$
Polynomial Division F323A2
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