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Simplifying 4214 \cdot 2^{-1} and (42)1(4 \cdot 2)^{-1} Using the Negative Exponent Definition

Apply the negative exponent definition to two expressions that combine multiplication with a negative exponent — one where the exponent applies to a single factor, and one where parentheses make the exponent apply to the entire product. The contrasting results illustrate why the order of operations matters when negative exponents and multiplication appear together.

421=24 \cdot 2^{-1} = 2: According to the order of operations, exponents are evaluated before multiplication. Apply the negative exponent definition to 212^{-1} first: 21=121=122^{-1} = \frac{1}{2^1} = \frac{1}{2}. The expression becomes 4124 \cdot \frac{1}{2}. Multiply: 412=24 \cdot \frac{1}{2} = 2.

(42)1=18(4 \cdot 2)^{-1} = \frac{1}{8}: The parentheses require the product inside to be simplified before the exponent is applied. Compute 42=84 \cdot 2 = 8 first, giving (8)1(8)^{-1}. Now apply the negative exponent definition: 81=181=188^{-1} = \frac{1}{8^1} = \frac{1}{8}.

Although both expressions involve the same numbers and operations, 421=24 \cdot 2^{-1} = 2 while (42)1=18(4 \cdot 2)^{-1} = \frac{1}{8}. Without parentheses, the exponent applies only to the factor directly beneath it (22). With parentheses, the entire product (424 \cdot 2) becomes the base of the negative exponent. This mirrors the general principle that parentheses change which quantity the exponent acts on.

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Updated 2026-04-21

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