Carcass wrote:
A perfect cube is an integer whose cube root is an integer. For example, 27, 64 and 125 are perfect cubes. If p and q are perfect cubes, which of the following will not necessarily be a perfect cube?
A. 8p
B. pq
C. pq + 27
D. -p
E. \((p - q)^6\)
Kudos for the right answer and explanation
Test some super easy values.
How about p = 1 and q = 1 (both are perfect cubes since 1³ = 1)
A. 8(1) = 8 = perfect cube
B. (1)(1) = 1 = perfect cube
C. (1)(1) + 27 = 28 = NOT a perfect cube
STOP TESTING VALUES. We've found an answer choice that is not necessarily a perfect cube
Answer:C