Question 32 of 480
Divide 4x3 - 3x + 1 by 2x - 1
- A. 2x2-x+1
- B. 2x2-x-1
- C. 2x2+x+1
- D. 2x2+x-1
Correct Answer:
D
Explanation
To solve the problem of dividing the polynomial \(4x^3 - 3x + 1\) by \(2x - 1\), we will use polynomial long division. Let's go through the steps in detail.
### Step-by-Step Explanation
1. **Set Up the Division**:
We write \(4x^3 - 3x + 1\) (the dividend) under the long division symbol and \(2x - 1\) (the divisor) outside.
\[
\begin{array}{r|l}
2x - 1 & 4x^3 + 0x^2 - 3x + 1 \\
\end{array}
\]
Note: We include \(0x^2\) to represent the missing \(x^2\) term.
2. **Divide the Leading Terms**:
Divide the leading term of the dividend \(4x^3\) by the leading term of the divisor \(2x\):
\[
\frac{4x^3}{2x} = 2x^2
\]
This is the first term of our quotient.
3. **Multiply and Subtract**:
Multiply \(2x^2\) by the entire divisor \(2x - 1\):
\[
2x^2(2x - 1) = 4x^3 - 2x^2
\]
Now, subtract this from the original polynomial:
\[
(4x^3 - 3x + 1) - (4x^3 - 2x^2) = 2x^2 - 3x + 1
\]
4. **Repeat the Process**:
Now, we repeat the process with the new polynomial \(2x^2 - 3x + 1\).
- Divide the leading term \(2x^2\) by \(2x\):
\[
\frac{2x^2}{2x} = x
\]
- Multiply \(x\) by the divisor:
\[
x(2x - 1) = 2x^2 - x
\]
- Subtract:
\[
(2x^2 - 3x + 1) - (2x^2 - x) = -2x + 1
\]
5. **Final Division**:
Now, we divide \(-2x + 1\) by \(2x - 1\).
- Divide the leading term \(-2x\) by \(2x\):
\[
\frac{-2x}{2x} = -1
\]
- Multiply \(-1\) by the divisor:
\[
-1(2x - 1) = -2x + 1
\]
- Subtract:
\[
(-2x + 1) - (-2x + 1) = 0
\]
6. **Conclusion**:
The division is complete, and we have no remainder. The quotient is:
\[
2x^2 + x - 1
\]
### Final Answer
The correct option is **D. \(2x^2 + x - 1\)**.
### Explanation of Other Options
- **A. \(2x^2 - x + 1\)**: This option has the wrong sign for the \(x\) term and the constant term is incorrect.
- **B. \(2x^2 - x - 1\)**: This option has the wrong sign for the constant term.
- **C. \(2x^2 + x + 1\)**: This option has the wrong sign for the constant term.
### Revision Summary
- Use polynomial long division to divide polynomials.
- Always align like terms and subtract carefully.
- Keep track of signs when multiplying and subtracting.
- The final quotient is the result of the division, with no remainder in this case.