Question
Download Solution PDFGiven that \(x = 4\sqrt{12} + 5\sqrt{27} - 3\sqrt{75} + \sqrt{300}\) and \(y = (2 + \sqrt{3})(2 - \sqrt{3}). \text{ If } \frac{x}{y} = a + b\sqrt{3},\) then what is the value of ?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFGiven:
\(x = 4\sqrt{12} + 5\sqrt{27} - 3\sqrt{75} + \sqrt{300}\)
\(y = (2 + \sqrt{3})(2 - \sqrt{3})\)
\(\frac{x}{y} = a + b\sqrt{3}\)
Formula used:
\(\sqrt{ab} = \sqrt{a}\sqrt{b}\)
\((a + b)(a - b) = a^2 - b^2\)
Calculation:
First, simplify the expression for x:
\(x = 4\sqrt{12} + 5\sqrt{27} - 3\sqrt{75} + \sqrt{300}\)
⇒ \(x = 4\sqrt{4 \times 3} + 5\sqrt{9 \times 3} - 3\sqrt{25 \times 3} + \sqrt{100 \times 3}\)
⇒ \(x = 4 \times 2\sqrt{3} + 5 \times 3\sqrt{3} - 3 \times 5\sqrt{3} + 10\sqrt{3}\)
⇒ \(x = 8\sqrt{3} + 15\sqrt{3} - 15\sqrt{3} + 10\sqrt{3}\)
⇒ \(x = (8 + 15 - 15 + 10)\sqrt{3}\)
⇒ \(x = 18\sqrt{3}\)
Next, simplify the expression for y:
\(y = (2 + \sqrt{3})(2 - \sqrt{3})\)
This is in the form (a + b)(a - b) = a2 - b2
⇒ \(y = 2^2 - (\sqrt{3})^2\)
⇒ \(y = 4 - 3\)
⇒ y = 1
Now, find the value of \(\frac{x}{y}\):
\(\frac{x}{y} = \frac{18\sqrt{3}}{1}\)
⇒ \(\frac{x}{y} = 18\sqrt{3}\)
We are given that \(\frac{x}{y} = a + b\sqrt{3}\).
So, \(18\sqrt{3} = a + b\sqrt{3}\)
By comparing the rational and irrational parts:
a = 0
b = 18
a + 2b = 0 + 2 × 18
⇒ a + 2b = 0 + 36
⇒ a + 2b = 36
∴ The correct answer is option 3.
Last updated on Jun 10, 2025
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