Let the given equation be [n/4]−[n/9]=2.
We are looking for the minimum positive integer value of n that satisfies this equation.
Let A=[n/4] and B=[n/9].
So, A−B=2, which means A=B+2.
By the definition of the greatest integer function:A≤n/4<A+1⟹4A≤n<4A+4B≤n/9<B+1⟹9B≤n<9B+9
Substitute A=B+2 into the first inequality:4(B+2)≤n<4(B+2)+44B+8≤n<4B+12
Now we have two inequalities for n:
9B≤n<9B+9
4B+8≤n<4B+12
For a common range for n to exist, there must be an overlap between these two intervals.
The lower bound for n is max(9B,4B+8).
The upper bound for n is min(9B+9,4B+12).
We need to find the smallest positive integer n. Let's test values for B (which must be a non-negative integer since n is positive).
Case 1: B = 0A=0+2=2.
From A=[n/4], we have 2≤n/4<3⟹8≤n<12.
From B=[n/9], we have 0≤n/9<1⟹0≤n<9.
For n to satisfy both, we need 8≤n<9. The only integer in this range is n=8.
Let's check n=8:[8/4]−[8/9]=2−0=2.
This satisfies the equation. So n=8 is a possible value. Since we started with the smallest possible B and found an integer n, this n is the minimum possible value.
Let's quickly check other values of B to ensure n=8 is indeed the minimum.Case 2: B = 1A=1+2=3.
From A=[n/4], we have 3≤n/4<4⟹12≤n<16.
From B=[n/9], we have 1≤n/9<2⟹9≤n<18.
For n to satisfy both, we need max(12,9)≤n<min(16,18), so 12≤n<16.
Possible integer values for n are 12,13,14,15. All of these are greater than 8.
Case 3: B = 2A=2+2=4.
From A=[n/4], we have 4≤n/4<5⟹16≤n<20.
From B=[n/9], we have 2≤n/9<3⟹18≤n<27.
For n to satisfy both, we need max(16,18)≤n<min(20,27), so 18≤n<20.
Possible integer values for n are 18,19. All of these are greater than 8.
Since we found n=8 for the smallest possible value of B=0, and subsequent values of B lead to larger n, the minimum possible value of n is 8.
The final answer is 8