Q. Use synthetic division to divide \(3x^3 – 11x^2 + 16x – 30\) by \(x – 3\).
Answer
\[
\begin{array}{r|rrrr}
3 & 3 & -11 & 16 & -30\\\hline
& & 9 & -6 & 30\\
& 3 & -2 & 10 & 0
\end{array}
\]
Bring down 3, multiply by 3 → 9, add → -2, multiply by 3 → -6, add → 10, multiply by 3 → 30, add → 0.
Quotient: \(3x^{2}-2x+10\), remainder: \(0\).
Detailed Explanation
Synthetic division of the polynomial by x−3 — step-by-step
- Write the polynomial and identify the divisor root.The dividend is \(3x^{3}-11x^{2}+16x-30\). The divisor is \(x-3\), whose root is \(3\).
- List the coefficients and set up the synthetic division table.The coefficients of the dividend (from highest degree to constant) are 3, −11, 16, −30. Place the root 3 to the left and the coefficients in a row:
3 | 3 -11 16 -30 | 9 -6 30 --------------------- 3 -2 10 0The numbers that will be written on the lower row are produced by the synthetic division steps shown next.
- Step-by-step operations (each operation explained separately).
- Bring down the first coefficient.Bring down the leading coefficient 3 to the bottom row. This becomes the first coefficient of the quotient.
Bottom row first entry: \(3\).
- Multiply and add to get the next bottom entry.Multiply the bottom entry 3 by the root 3: \(3 \times 3 = 9\).
Add this product to the next coefficient in the top row: \(-11 + 9 = -2\).
Bottom row second entry: \(-2\).
- Repeat multiply and add.Multiply the new bottom entry \(-2\) by the root 3: \(-2 \times 3 = -6\).
Add to the next coefficient: \(16 + (-6) = 10\).
Bottom row third entry: \(10\).
- Final multiply and add to obtain the remainder.Multiply the bottom entry 10 by the root 3: \(10 \times 3 = 30\).
Add to the final coefficient: \(-30 + 30 = 0\).
The final bottom entry is the remainder: \(0\).
- Bring down the first coefficient.Bring down the leading coefficient 3 to the bottom row. This becomes the first coefficient of the quotient.
- Form the quotient and state the remainder.The bottom row entries (except the final remainder) are the coefficients of the quotient polynomial, in descending powers of x. They are \(3\), \(-2\), and \(10\), which correspond to the quotient
\(3x^{2} – 2x + 10\).
The remainder is \(0\).
Therefore, dividing \(3x^{3}-11x^{2}+16x-30\) by \(x-3\) yields the quotient \(3x^{2}-2x+10\) with remainder \(0\).
- Optional check (value at the root).Evaluate the polynomial at \(x=3\) to confirm the remainder is zero:
\(f(3)=3(3)^{3}-11(3)^{2}+16(3)-30=81-99+48-30=0\).
This confirms the remainder is \(0\) and that \(x-3\) is a factor.
Final result: Quotient is \(3x^{2}-2x+10\) and remainder is \(0\).
Algebra FAQs
What is synthetic division?
How do I set up synthetic division for \(3x^3-11x^2+16x-30\) divided by \(x-3\)?
What is the quotient and remainder for this division?
What if the polynomial has a missing term, e.g., no \(x^2\) term?.
Why do we use \(c=3\) for divisor \(x-3\)?
How does synthetic division connect to the Remainder and Factor Theorems?
Can synthetic division be used when the divisor is not of the form \(x-c\)?
What if the leading coefficient isn’t 1 — does synthetic division still work?
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