题目
If p and q are positive integers greater than 1 and p > q, for how many pair(s) of values is ?
解析
我们需要找出所有满足条件的正整数对\( (p, q) \)(\( p > q > 1 \)),使得\( p^q \geq q^p \)。
我们可以通过**枚举小数值**(因为当\( p, q \)增大时,\( q^p \)的增长速度远快于\( p^q \))来验证:
1. 当\( q = 2 \)时:
- \( p = 3 \):\( 3^2 = 9 \),\( 2^3 = 8 \),满足\( 9 \geq 8 \);
- \( p = 4 \):\( 4^2 = 16 \),\( 2^4 = 16 \),满足\( 16 \geq 16 \);
- \( p = 5 \):\( 5^2 = 25 \),\( 2^5 = 32 \),不满足;
- \( p \geq 5 \)时,\( 2^p \)增长远快于\( p^2 \),均不满足。
2. 当\( q = 3 \)时:
- \( p = 4 \):\( 4^3 = 64 \),\( 3^4 = 81 \),不满足;
- \( p \geq 4 \)时,\( 3^p \)增长远快于\( p^3 \),均不满足。
3. 当\( q \geq 4 \)时:
对于\( p > q \geq 4 \),\( q^p \)的增长速度远超过\( p^q \)(例如\( q=4, p=5 \):\( 5^4=625 \),\( 4^5=1024 \),不满足),因此无满足条件的数对。
综上,满足条件的数对只有\( (3, 2) \)和\( (4, 2) \),共2对。
答案:C