ACT Math · Number operations and exponents

Which expression is equivalent to (2x^-3y²)^-2 for x, y ≠ 0?

Which expression is equivalent to (2x−3y2)−2(2x^{-3}y^2)^{-2} for x,y≠0x, y \neq 0?

Answer and explanation

Answer: F: (x^6)/(4y^4)

Apply the outer exponent −2-2 to each factor: 2−2=142^{-2}=\frac{1}{4}, (x−3)−2=x6(x^{-3})^{-2}=x^{6}, and (y2)−2=y−4=1y4(y^2)^{-2}=y^{-4}=\frac{1}{y^4}. Combined, the expression is x64y4\frac{x^6}{4y^4}, choice F. Choice G has the xx term in the denominator and puts 44 in the numerator, so it mishandles every sign. Choice H keeps x−6x^{-6}, so the exponent of xx was multiplied incorrectly (−3⋅−2=+6-3\cdot-2=+6, not −6-6). Choice J drops the negative outer exponent, which squares the coefficient and flips nothing. Multiply exponents carefully, with signs.

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