A rational expression is a fraction in which both the numerator and the denominator are polynomials.
Let's examine each option:
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9x−48+x√: This expression is not presented correctly, but based on my understanding, if it were meant to be a simplified rational expression, it doesn’t appear to be in the form of a polynomial over a polynomial due to the presence of the square root.
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x32+52x9: This doesn't appear to be in standard form, but if it were meant to be \( \frac{x^{\frac{3}{2}} + \frac{5}{2}x^9}{something} \), then we'd need the denominator to determine if it's a rational expression. Without a denominator shown, we can't confirm it's a rational expression.
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5.32x−1: This appears to be in the form of a fraction, likely \( \frac{5.3}{2x - 1} \). Here, both the numerator (5.3, which can be treated as a constant polynomial) and the denominator (2x - 1, which is a polynomial) fit the definition of a rational expression.
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8x2+70: This expression is simply a polynomial (without a denominator), so it is not a rational expression by itself.
Based on these analyses, the most likely choice that represents a rational expression is:
5.32x−1 (interpreted as \( \frac{5.3}{2x - 1} \)).