absolute easy

首先要知道 absolute 的意思是指把該值的負號除去(如果是該值是負數的話)

現在-1/6<=y<=1
請閣下想像一條數線去代表y的值
(會看到y是介乎-1/6至到1中間)

現在為y加上absolute sign
y的正數部分不變
而負的部分因為加上absolute sign而變正數
(-1/6到-0會變成0到+1/6，現在|y|的最小值是0)
另外，由於1>1/6，所以|y|的最大值是1

所以0<=|y|<=1

PS:這個只是邏輯問題，只要細心想，不熟數學的人都會明白

The answer is 0<=| k| <= 1.
Divide the range of value of k into two parts:
Part 1: 0<= k <= 1
It is clear that 0<= |k| <= 1 ...(*),
since k is positive, the range of |k| is also the same.
Part 2: -1/3 <= k < 0
As k is negative, therefore range of |k| should be
0 < |k| <= 1/3 ...(#)
Combining (*) and (#), the range of |k| is
0<= |k| <= 1