坐標平面上,x坐標與y坐標均為整數的點稱為格子點。試問在函數圖形
y = log2 x、x軸與直線 x = 61/2 所圍有界區域的內部(不含邊界)共有多少個格子點?
(1) 88
(2) 89
(3) 90
(4) 91
(5) 92
Thought
Mapping the area
I’m analyzing the region enclosed by y = log2(x), the x-axis, and x = 61/2. This area spans from 1 to 61/2 on the x-axis, with y ranging from 0 to log2(x).
Adjusting my thinking
Note that for x in (0,1), log2(x) is negative, so the region above the x-axis and below log2(x) only starts from x = 1 onwards.
Breaking down the grid
I’m focusing on the interior grid points by noting 1 < a < 61/2 and 0 < b < log2(a). This results in a range of valid x coordinates from 2 to 30.
Shifting my approach
Focusing on integer y values where 1 <= b <= floor(log2(a))-1 ensures y is strictly less than log2(a), providing valid y coordinates for each integer x within the specified range.
Considering integer constraints
OK, let's think this through: I'm counting integers b such that b < log2(a). If log2(a) equals an integer, b ranges from 1 to that integer - 1; otherwise, b ranges just up to floor(log2(a)).
Mapping valid b values
I’m gathering info on valid b values for each a by checking if log2(a) is an integer. If it isn't, b ranges from 1 to floor(log2(a)).
Investigating integer b values
I'm digging into how valid b values for each a are determined by floor(log2(a)), checking if a is a power of 2, and counting solutions accordingly.
Identifying power of 2 intervals
Now I’m pinpointing integral intervals for a, specifically acceptable values like 2, 4, 8, and 16, to ensure b < log2(a). Each interval yields a specific number of valid solutions for b.
Mapping out valid solutions
I’m counting valid solutions for each a: for 3 to 16, I’m tallying integer b values that satisfy b < log2(a), which totals 29 solutions across all intervals.
Discovering solutions
I’m adding the valid integer b values for each non-power of 2 a, noting that as a approaches 30, the number of solutions increases, starting from 3 solutions for a=16.
Figuring out solutions
OK, let me see. For each a between 17 and 30, excluding powers of 2, I’m figuring out 4 valid integer b solutions. This approach gives a total of 56 solutions.
Analyzing partial sums
I’m piecing together the partial sums for each integer a, including 3 to 16 and 17 to 30, to reach a total of 34 valid integer solutions for b.
Thought about grid points in region for 27 seconds