1. **State the problem:** Rationalise the denominator of the expression $$\frac{7 - \sqrt{5}}{\sqrt{5} - 2}$$ and express the answer in the form $$a + b\sqrt{5}$$.
2. **Formula and rule:** To rationalise a denominator with a surd, multiply numerator and denominator by the conjugate of the denominator. The conjugate of $$\sqrt{5} - 2$$ is $$\sqrt{5} + 2$$.
3. **Multiply numerator and denominator by the conjugate:**
$$\frac{7 - \sqrt{5}}{\sqrt{5} - 2} \times \frac{\sqrt{5} + 2}{\sqrt{5} + 2} = \frac{(7 - \sqrt{5})(\sqrt{5} + 2)}{(\sqrt{5} - 2)(\sqrt{5} + 2)}$$
4. **Simplify the denominator using difference of squares:**
$$ (\sqrt{5})^2 - (2)^2 = 5 - 4 = 1 $$
5. **Expand the numerator:**
$$ (7)(\sqrt{5}) + 7 \times 2 - \sqrt{5} \times \sqrt{5} - \sqrt{5} \times 2 = 7\sqrt{5} + 14 - 5 - 2\sqrt{5} $$
6. **Combine like terms in numerator:**
$$ (7\sqrt{5} - 2\sqrt{5}) + (14 - 5) = 5\sqrt{5} + 9 $$
7. **Write the final expression:**
$$ \frac{5\sqrt{5} + 9}{1} = 9 + 5\sqrt{5} $$
**Final answer:** $$9 + 5\sqrt{5}$$
Rationalise Denominator 46Fe5F
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