Question 48 of 480
If \(\frac{(2\sqrt{3}-\sqrt{2})}{(\sqrt{3}+2\sqrt{2})} = m +n\sqrt{6}\), find the values of m and n respectively.
- A. 1, -2
- B. -2, 1
- C. \(\frac{-2}{5}\), 1
- D. 2, 3/5
Correct Answer:
B
Explanation
To solve the equation
\[
\frac{(2\sqrt{3}-\sqrt{2})}{(\sqrt{3}+2\sqrt{2})} = m + n\sqrt{6},
\]
we need to simplify the left-hand side and express it in the form \(m + n\sqrt{6}\).
### Step 1: Rationalizing the Denominator
To simplify the fraction, we can multiply the numerator and the denominator by the conjugate of the denominator. The conjugate of \((\sqrt{3} + 2\sqrt{2})\) is \((\sqrt{3} - 2\sqrt{2})\). Thus, we have:
\[
\frac{(2\sqrt{3}-\sqrt{2})(\sqrt{3}-2\sqrt{2})}{(\sqrt{3}+2\sqrt{2})(\sqrt{3}-2\sqrt{2})}.
\]
### Step 2: Simplifying the Denominator
The denominator simplifies as follows:
\[
(\sqrt{3})^2 - (2\sqrt{2})^2 = 3 - 8 = -5.
\]
### Step 3: Simplifying the Numerator
Now, we simplify the numerator:
\[
(2\sqrt{3}-\sqrt{2})(\sqrt{3}-2\sqrt{2}) = 2\sqrt{3} \cdot \sqrt{3} - 2\sqrt{3} \cdot 2\sqrt{2} - \sqrt{2} \cdot \sqrt{3} + \sqrt{2} \cdot 2\sqrt{2}.
\]
Calculating each term:
1. \(2\sqrt{3} \cdot \sqrt{3} = 2 \cdot 3 = 6\),
2. \(-2\sqrt{3} \cdot 2\sqrt{2} = -4\sqrt{6}\),
3. \(-\sqrt{2} \cdot \sqrt{3} = -\sqrt{6}\),
4. \(\sqrt{2} \cdot 2\sqrt{2} = 2 \cdot 2 = 4\).
Combining these results, we have:
\[
6 - 4\sqrt{6} - \sqrt{6} + 4 = 10 - 5\sqrt{6}.
\]
### Step 4: Putting It All Together
Now, substituting back into our fraction, we get:
\[
\frac{10 - 5\sqrt{6}}{-5} = -2 + \sqrt{6}.
\]
This can be rewritten as:
\[
-2 + 1\sqrt{6}.
\]
### Step 5: Identifying \(m\) and \(n\)
From the expression \(-2 + 1\sqrt{6}\), we can identify:
- \(m = -2\)
- \(n = 1\)
### Conclusion
Thus, the values of \(m\) and \(n\) are:
\[
m = -2, \quad n = 1.
\]
The correct option is **B. -2, 1**.
### Explanation of Other Options
- **Option A (1, -2)**: This is incorrect because the values of \(m\) and \(n\) do not match our derived values.
- **Option C \(\left(\frac{-2}{5}, 1\right)\)**: This is incorrect because \(m\) is not \(\frac{-2}{5}\); it is \(-2\).
- **Option D (2, \frac{3}{5})**: This is incorrect as neither \(m\) nor \(n\) matches the derived values.
### Revision Summary
- Rationalize the denominator by multiplying by the conjugate.
- Simplify both the numerator and denominator carefully.
- Combine like terms to express the result in the form \(m + n\sqrt{6}\).
- Identify \(m\) and \(n\) from the simplified expression.