We are given that $\frac{\sqrt{3} + \sqrt{5}}{\sqrt{5}} = x + y\sqrt{15}$, and we need to find the value of $x + y$.

AlgebraSimplificationRadicalsRationalizationEquationsAlgebraic Manipulation
2025/4/10

1. Problem Description

We are given that 3+55=x+y15\frac{\sqrt{3} + \sqrt{5}}{\sqrt{5}} = x + y\sqrt{15}, and we need to find the value of x+yx + y.

2. Solution Steps

First, we simplify the left-hand side of the equation by splitting the fraction:
3+55=35+55=35+1\frac{\sqrt{3} + \sqrt{5}}{\sqrt{5}} = \frac{\sqrt{3}}{\sqrt{5}} + \frac{\sqrt{5}}{\sqrt{5}} = \frac{\sqrt{3}}{\sqrt{5}} + 1
Now, we rationalize the denominator of the first term:
35=3555=355=155\frac{\sqrt{3}}{\sqrt{5}} = \frac{\sqrt{3}}{\sqrt{5}} \cdot \frac{\sqrt{5}}{\sqrt{5}} = \frac{\sqrt{3} \cdot \sqrt{5}}{5} = \frac{\sqrt{15}}{5}
So, we have:
3+55=155+1=1+1515\frac{\sqrt{3} + \sqrt{5}}{\sqrt{5}} = \frac{\sqrt{15}}{5} + 1 = 1 + \frac{1}{5}\sqrt{15}
Comparing this with x+y15x + y\sqrt{15}, we have x=1x = 1 and y=15y = \frac{1}{5}.
Therefore, x+y=1+15=55+15=65x + y = 1 + \frac{1}{5} = \frac{5}{5} + \frac{1}{5} = \frac{6}{5}.
Converting this improper fraction to a mixed number gives 1151\frac{1}{5}.

3. Final Answer

1151\frac{1}{5}
The answer is C.

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