I think I’m confusing the index laws when the bases match versus when an exponent is outside parentheses-what’s the correct rule for 2^3 × 2^2 compared to (2^3)^2? I’ve messed this up on quizzes before and want to make sure I’m not missing something obvious.
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3 Responses
Totally easy to mix up-I do it too: when multiplying the same base, add exponents; when raising a power to a power, multiply exponents. So 2^3 × 2^2 = 2^(3+2) = 2^5 = 32, while (2^3)^2 = 2^(3·2) = 2^6 = 64.
When the bases match and you multiply, the exponents add: 2^3 × 2^2 = 2^(3+2) = 2^5 = 32.
But a power of a power makes them multiply: (2^3)^2 = 2^(3·2) = 2^6 = 64.
Easy to mix up-same symbols, different jobs. Here’s the rule of thumb: when you’re multiplying matching bases (like 2^3 × 2^2), you add the exponents: a^m × a^n = a^(m+n). When you’ve got a power raised to another power (like (2^3)^2), you multiply the exponents: (a^m)^n = a^(m·n). Side-by-side means add, stacked means multiply.
Quick check with your numbers:
– 2^3 × 2^2 = (2·2·2) × (2·2) = five 2’s multiplied = 2^5 = 32.
– (2^3)^2 = (2·2·2)^2 = (2·2·2)(2·2·2) = six 2’s multiplied = 2^6 = 64.
If you like a mental trick: imagine how many 2’s you’re actually stringing together. Side-by-side groups just join up (add), stacking a power on a power doubles/triples/etc. the count (multiply).