GMAT Practice Question: If a > 0, b = 2a, and c = 2b, which of the following is equivalent to a^b b^c ?
Question
If a > 0, b = 2a, and c = 2b, which of the following is equivalent to a^b b^c ?
- (2a^4)^a
- (2a^6)^a
- (2a^8)^a
- (16a^6)^a
- (16a^8)^a
Topics: exponents, expression formulas
Solution
Step 1
We first express the given relationships of b and c in terms of a
b = 2a c = 2b
Step 2
We substitute these expressions for b and c into a^b b^c
a^b \times b^c = a^{2a} \times (2a)^{4a}
Step 3
We expand (2a)^{4a} by raising each factor to the power 4a
(2a)^{4a} = 2^{4a} \times a^{4a}
Step 4
We apply \textbf{Multiplying Exponents of the Same Base} to combine a^{2a} and a^{4a}
a^{2a} \times a^{4a} = a^{2a + 4a} = a^{6a}
Step 5
We rewrite 2^{4a} and a^{6a} using \textbf{Exponents of Exponents} and combine them
2^{4a} = (2^4)^a = 16^a a^{6a} = (a^6)^a 2^{4a} \times a^{6a} = (16 \times a^6)^a
Answer
D
