Algebra 2 / Unit 3: Polynomial Functions
3.3 Long and Synthetic Division
Notes
Divide polynomials like numbers: $\displaystyle \frac{\text{dividend}}{\text{divisor}} = \text{quotient} + \frac{\text{remainder}}{\text{divisor}}$.
- Long division works for any divisor. Fill in missing powers with 0 terms.
- Synthetic division is a shortcut when dividing by $x - c$. Use $c$ (so for $x + 2$, use $-2$).
- Synthetic steps: bring down the first coefficient, multiply by $c$, add to the next coefficient, repeat. The last number is the remainder.
- Example: $(x^2 + 7x + 10) \div (x + 2) = x + 5$, remainder 0.
Practice
Divide $(x^2 + 5x + 6) \div (x + 2)$.
$x^2 + 5x + 6 = (x + 2)(x + 3)$.
Use synthetic division to divide $x^3 - 2x^2 - 5x + 6$ by $x - 3$.
With 3: bring down 1; $-2 + 3 = 1$; $-5 + 3 = -2$; $6 - 6 = 0$.
Divide $2x^3 + 3x^2 - x + 4$ by $x + 1$.
Use $-1$: $2$; $3 - 2 = 1$; $-1 - 1 = -2$; $4 + 2 = 6$.
Ready for more? Take the Unit 3 test.