Question 286 of 480
Simplify the expression \(3(x + 4) - 2(2x - 5)\). What is the resulting expression?
- \(x + 22\)
- \(-x + 22\)
- \(x + 10\)
- \(5x - 2\)
Correct Answer:
B
Explanation
To simplify the expression \(3(x + 4) - 2(2x - 5)\), we will follow a step-by-step approach.
### Step 1: Distribute the coefficients
First, we need to distribute the numbers outside the parentheses to the terms inside the parentheses.
1. For the first part, \(3(x + 4)\):
- Multiply \(3\) by \(x\): \(3 \cdot x = 3x\)
- Multiply \(3\) by \(4\): \(3 \cdot 4 = 12\)
- So, \(3(x + 4) = 3x + 12\)
2. For the second part, \(-2(2x - 5)\):
- Multiply \(-2\) by \(2x\): \(-2 \cdot 2x = -4x\)
- Multiply \(-2\) by \(-5\): \(-2 \cdot -5 = 10\) (Note: multiplying two negatives gives a positive)
- So, \(-2(2x - 5) = -4x + 10\)
### Step 2: Combine the results
Now we can combine the results from both distributions:
\[
3(x + 4) - 2(2x - 5) = (3x + 12) + (-4x + 10)
\]
### Step 3: Combine like terms
Next, we will combine the like terms (the terms with \(x\) and the constant terms):
1. Combine the \(x\) terms:
- \(3x - 4x = -1x\) or simply \(-x\)
2. Combine the constant terms:
- \(12 + 10 = 22\)
Putting it all together, we have:
\[
-x + 22
\]
### Final Result
Thus, the simplified expression is:
\[
-x + 22
\]
### Answer
The correct option is **B. \(-x + 22\)**.
### Explanation of Other Options
- **Option A: \(x + 22\)**: This option is incorrect because it suggests that the coefficient of \(x\) is positive, which contradicts our calculation where we found it to be \(-x\).
- **Option C: \(x + 10\)**: This option is incorrect as it not only has the wrong coefficient for \(x\) but also has the wrong constant term. The constant term should be \(22\), not \(10\).
- **Option D: \(5x - 2\)**: This option is incorrect because it suggests a completely different expression. The coefficients and constants do not match our simplified expression at all.
### Common Pitfalls
- **Distributing Negatives**: A common mistake is to forget to distribute the negative sign correctly when dealing with expressions like \(-2(2x - 5)\). Always remember that a negative sign will change the signs of the terms inside the parentheses.
- **Combining Like Terms**: Ensure that you only combine terms that are similar (i.e., terms with \(x\) and constant terms separately).
### Revision Summary
- Distribute coefficients carefully to each term inside parentheses.
- Combine like terms systematically to simplify expressions.
- Pay attention to signs, especially when distributing negatives.
- Always double-check your final expression against the options provided.