Simplify \(\frac{1 - 2\sqrt{5}}{2 + 3\sqrt{2}}\).
FURTHER MATHEMATICS
WAEC 2015
Simplify \(\frac{1 - 2\sqrt{5}}{2 + 3\sqrt{2}}\).
- A. \(14(2\sqrt{2} + 6\sqrt{5} - 4\sqrt{10})\)
- B. \(\frac{1}{14}(2 - 3\sqrt{2} - 4\sqrt{5} - 6\sqrt{10})\)
- C. \(\frac{1}{14}(3\sqrt{2} + 4\sqrt{5} - 6\sqrt{10} - 2)\)
- D. \(14(2 + 3\sqrt{2} - 6\sqrt{5} + 4\sqrt{10})\)
Correct Answer: C. \(\frac{1}{14}(3\sqrt{2} + 4\sqrt{5} - 6\sqrt{10} - 2)\)
Explanation
\(\frac{1 - 2\sqrt{5}}{2 + 3\sqrt{2}} = (\frac{1 - 2\sqrt{5}}{2 + 3\sqrt{2}})(\frac{2 - 3\sqrt{2}}{2 - 3\sqrt{2}})\)
= \(\frac{2 - 3\sqrt{2} - 4\sqrt{5} + 6\sqrt{10}}{4 - 6\sqrt{2} + 6\sqrt{2} - 18}\)
= \(\frac{2 - 3\sqrt{2} - 4\sqrt{5} + 6\sqrt{10}}{-14}\)
= \(\frac{1}{14}(3\sqrt{2} + 4\sqrt{5} - 2 - 6\sqrt{10})\) (dividing through with the minus sign)
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