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Simplifying (57)2\left(\frac{5}{7}\right)^{-2} and (2xy)3\left(-\frac{2x}{y}\right)^{-3} Using the Quotient to a Negative Exponent Property

Apply the Quotient to a Negative Exponent Property to simplify two expressions — one with a purely numerical fraction and one with an algebraic fraction that includes a negative sign.

(57)2=4925\left(\frac{5}{7}\right)^{-2} = \frac{49}{25}: The base is the fraction 57\frac{5}{7} and the exponent is 2-2. Apply the property (ab)n=(ba)n\left(\frac{a}{b}\right)^{-n} = \left(\frac{b}{a}\right)^n: take the reciprocal of the fraction and make the exponent positive, giving (75)2\left(\frac{7}{5}\right)^2. Evaluate by squaring numerator and denominator: 7252=4925\frac{7^2}{5^2} = \frac{49}{25}.

(2xy)3=y38x3\left(-\frac{2x}{y}\right)^{-3} = -\frac{y^3}{8x^3}: The base is 2xy-\frac{2x}{y} and the exponent is 3-3. Apply the property: take the reciprocal and change the sign of the exponent, giving (y2x)3\left(-\frac{y}{2x}\right)^3. Raise each component to the third power. Because the exponent 33 is odd, the negative sign is preserved: (1)3y3(2x)3=y38x3(-1)^3 \cdot \frac{y^3}{(2x)^3} = -\frac{y^3}{8x^3}.

Part (a) demonstrates the basic procedure with a numerical fraction. Part (b) extends it to a variable fraction with a negative sign, showing that an odd exponent keeps the result negative after the reciprocal step.

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Updated 2026-04-21

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