Use exponent rules and rewrite rational exponents in radical form (and vice versa). | Equivalent expressions | SAT Math

Exponent rules let you rewrite products, quotients, and powers of same-base expressions. Rational exponents connect exponents to radicals: $𝑥 1 𝑛 = 𝑛 \sqrt 𝑥$ .

核心知识

Multiplying same-base terms adds exponents, dividing subtracts them, and raising a power to a power multiplies them. A rational exponent $𝑥 𝑚 𝑛$ means $𝑛 \sqrt 𝑥 𝑚$ —the denominator is the root, the numerator is the power.

深入理解

Three rules handle most SAT exponent questions:

Core rules:

Product rule: $𝑥 𝑎 \cdot 𝑥 𝑏 = 𝑥 𝑎 + 𝑏$
Quotient rule: $𝑥 𝑎 𝑥 𝑏 = 𝑥 𝑎 - 𝑏$
Power rule: $(𝑥 𝑎) 𝑏 = 𝑥 𝑎 𝑏$

Rational exponents are another notation for radicals. The denominator of the exponent is the index of the radical, and the numerator is the power: $𝑥 34 = 4 \sqrt 𝑥 3$ . Converting between these forms is a common question type.

When simplifying, convert everything to the same form first. If the expression mixes radicals and exponents, rewrite all radicals as fractional exponents, simplify using the rules above, then convert back if the answer choices use radical form.

Negative exponents flip the base to the denominator: $𝑥 - 𝑎 = 1 𝑥 𝑎$ . This comes up when quotient-rule subtraction yields a negative result.

分步讲解

Convert any radicals to rational exponents: $𝑛 \sqrt 𝑥 𝑚 = 𝑥 𝑚 𝑛$ .
Apply product, quotient, and power rules to combine or simplify exponents.
Find a common denominator when adding or subtracting fractional exponents.
Convert the result to match the answer choice format (rational exponent or radical).

常见误解

Multiplying exponents when bases are being multiplied (should add): writing $𝑥 2 \cdot 𝑥 3 = 𝑥 6$ instead of $𝑥 5$ .
Confusing the numerator and denominator of rational exponents: interpreting $𝑥 34$ as $3 \sqrt 𝑥 4$ instead of $4 \sqrt 𝑥 3$ .
Adding exponents when dividing instead of subtracting: $𝑥 5 𝑥 2 = 𝑥 7$ instead of $𝑥 3$ .

题目

示例解析

For $𝑥 > 0$ , which expression is equivalent to $𝑥 2 \cdot \sqrt 𝑥 3 \sqrt 𝑥$ ?

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