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Which of the following is the radical expression of [tex]$a^{\frac{5}{7}}$[/tex]?

A. [tex]\sqrt[5]{a^7}[/tex]
B. [tex]\sqrt[7]{a^5}[/tex]
C. [tex]5 a^7[/tex]
D. [tex]7 a^5[/tex]


Sagot :

To determine the correct radical expression for [tex]\( a^{\frac{5}{7}} \)[/tex], let's examine the options provided.

### Step-by-Step Analysis:

1. Understanding [tex]\( a^{\frac{5}{7}} \)[/tex]:
The expression [tex]\( a^{\frac{5}{7}} \)[/tex] represents a number raised to the power of a fraction. This fraction suggests that we could write it as a radical (or root) expression, generally represented as [tex]\( \sqrt[n]{a^m} \)[/tex], where [tex]\( n \)[/tex] is the denominator and [tex]\( m \)[/tex] is the numerator of the fraction.

2. Converting [tex]\( a^{\frac{5}{7}} \)[/tex] to Radical Form:
The general rule for converting a fractional exponent [tex]\( a^{\frac{m}{n}} \)[/tex] into radical form is:
[tex]\[ a^{\frac{m}{n}} = \sqrt[n]{a^m} \][/tex]
Therefore:
[tex]\[ a^{\frac{5}{7}} = \sqrt[7]{a^5} \][/tex]

3. Comparing with Given Options:

- Option 1: [tex]\( \sqrt[5]{a^7} \)[/tex]
- This corresponds to [tex]\( a^{\frac{7}{5}} \)[/tex], not [tex]\( a^{\frac{5}{7}} \)[/tex].

- Option 2: [tex]\( \sqrt[7]{a^5} \)[/tex]
- This indeed matches our derived radical form of [tex]\( a^{\frac{5}{7}} \)[/tex].

- Option 3: [tex]\( 5 a^7 \)[/tex]
- This is a linear combination of multiplying 5 and [tex]\( a^7 \)[/tex], and does not involve transforming the exponent in fractions.

- Option 4: [tex]\( 7 a^5 \)[/tex]
- This also is a linear combination and does not represent the radical form of [tex]\( a^{\frac{5}{7}} \)[/tex].

### Conclusion:
The correct radical expression for [tex]\( a^{\frac{5}{7}} \)[/tex] is indeed:
[tex]\[ \sqrt[7]{a^5} \][/tex]

Therefore, the correct option is:

Option 2: [tex]\( \sqrt[7]{a^5} \)[/tex]