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Express [tex]\(\frac{5 - 2 \sqrt{10}}{3 \sqrt{5} + \sqrt{2}}\)[/tex] in the form [tex]\(m \sqrt{2} + n \sqrt{5}\)[/tex], where [tex]\(m\)[/tex] and [tex]\(n\)[/tex] are rational numbers.

Sagot :

To express [tex]\(\frac{5-2 \sqrt{10}}{3 \sqrt{5}+\sqrt{2}}\)[/tex] in the form [tex]\(m \sqrt{2}+n \sqrt{5}\)[/tex], we follow these steps:

1. Identify the Conjugate:
To rationalize the denominator, we multiply both the numerator and the denominator by the conjugate of the denominator. The conjugate of [tex]\(3 \sqrt{5} + \sqrt{2}\)[/tex] is [tex]\(3 \sqrt{5} - \sqrt{2}\)[/tex].

2. Multiply by the Conjugate:
Multiply the numerator and denominator by [tex]\(3 \sqrt{5} - \sqrt{2}\)[/tex]:
[tex]\[ \frac{5-2 \sqrt{10}}{3 \sqrt{5}+\sqrt{2}} \cdot \frac{3 \sqrt{5} - \sqrt{2}}{3 \sqrt{5} - \sqrt{2}} \][/tex]

3. Expand the Numerator:
Expand the product in the numerator:
[tex]\[ (5 - 2 \sqrt{10})(3 \sqrt{5} - \sqrt{2}) \][/tex]
Distributing each term, we get:
[tex]\[ 5 \cdot 3 \sqrt{5} - 5 \cdot \sqrt{2} - 2 \sqrt{10} \cdot 3 \sqrt{5} + 2 \sqrt{10} \cdot \sqrt{2} \][/tex]
Simplifying each term, we have:
[tex]\[ 15 \sqrt{5} - 5 \sqrt{2} - 6 \sqrt{50} + 2 \sqrt{20} \][/tex]
Since [tex]\(\sqrt{50} = 5 \sqrt{2}\)[/tex] and [tex]\(\sqrt{20} = 2 \sqrt{5}\)[/tex], we can further simplify:
[tex]\[ 15 \sqrt{5} - 5 \sqrt{2} - 6 \cdot 5 \sqrt{2} + 2 \cdot 2 \sqrt{5} \][/tex]
[tex]\[ 15 \sqrt{5} - 5 \sqrt{2} - 30 \sqrt{2} + 4 \sqrt{5} \][/tex]
Collecting like terms, we get:
[tex]\[ 19 \sqrt{5} - 35 \sqrt{2} \][/tex]

4. Expand the Denominator:
Expand the product in the denominator:
[tex]\[ (3 \sqrt{5} + \sqrt{2})(3 \sqrt{5} - \sqrt{2}) \][/tex]
This is a difference of squares, so it simplifies to:
[tex]\[ (3 \sqrt{5})^2 - (\sqrt{2})^2 \][/tex]
Calculating each term, we get:
[tex]\[ 9 \cdot 5 - 2 \][/tex]
[tex]\[ 45 - 2 = 43 \][/tex]

5. Form the Rationalized Expression:
We now have:
[tex]\[ \frac{19 \sqrt{5} - 35 \sqrt{2}}{43} \][/tex]

6. Express in the Desired Form:
Separate the terms to express it in the form [tex]\(m \sqrt{2} + n \sqrt{5}\)[/tex]:
[tex]\[ \frac{19 \sqrt{5} - 35 \sqrt{2}}{43} = \frac{19 \sqrt{5}}{43} - \frac{35 \sqrt{2}}{43} \][/tex]

Thus, the expression [tex]\(\frac{5-2 \sqrt{10}}{3 \sqrt{5}+\sqrt{2}}\)[/tex] in the form [tex]\(m \sqrt{2}+n \sqrt{5}\)[/tex] is:
[tex]\[ m = -\frac{35}{43}, \quad n = \frac{19}{43} \][/tex]
So, we have:
[tex]\[ \boxed{\frac{5-2 \sqrt{10}}{3 \sqrt{5}+\sqrt{2}} = -\frac{35 \sqrt{2}}{43} + \frac{19 \sqrt{5}}{43}} \][/tex]