The problem is to analyze the function $y = |x+2| - |2x-4|$. The solution involves finding the critical points where the expressions inside the absolute values are zero and then analyzing the function in the intervals defined by these critical points. The critical points are found by solving $x+2 = 0$ and $2x-4 = 0$.

AlgebraAbsolute ValuePiecewise FunctionsFunction Analysis
2025/5/12

1. Problem Description

The problem is to analyze the function y=x+22x4y = |x+2| - |2x-4|. The solution involves finding the critical points where the expressions inside the absolute values are zero and then analyzing the function in the intervals defined by these critical points. The critical points are found by solving x+2=0x+2 = 0 and 2x4=02x-4 = 0.

2. Solution Steps

First, we find the critical points.
x+2=0    x=2x+2 = 0 \implies x = -2
2x4=0    2x=4    x=22x-4 = 0 \implies 2x = 4 \implies x = 2
Now, we analyze the function in the three intervals defined by the critical points x=2x = -2 and x=2x = 2:
Interval 1: x<2x < -2
In this interval, x+2<0x+2 < 0 and 2x4<02x-4 < 0. Therefore, x+2=(x+2)|x+2| = -(x+2) and 2x4=(2x4)|2x-4| = -(2x-4).
y=(x+2)((2x4))=x2+2x4=x6y = -(x+2) - (-(2x-4)) = -x-2 + 2x-4 = x - 6
Interval 2: 2x<2-2 \le x < 2
In this interval, x+20x+2 \ge 0 and 2x4<02x-4 < 0. Therefore, x+2=x+2|x+2| = x+2 and 2x4=(2x4)|2x-4| = -(2x-4).
y=(x+2)((2x4))=x+2+2x4=3x2y = (x+2) - (-(2x-4)) = x+2 + 2x-4 = 3x - 2
Interval 3: x2x \ge 2
In this interval, x+2>0x+2 > 0 and 2x402x-4 \ge 0. Therefore, x+2=x+2|x+2| = x+2 and 2x4=2x4|2x-4| = 2x-4.
y=(x+2)(2x4)=x+22x+4=x+6y = (x+2) - (2x-4) = x+2 - 2x+4 = -x + 6
So the function can be defined as:
y={x6if x<23x2if 2x<2x+6if x2y = \begin{cases} x - 6 & \text{if } x < -2 \\ 3x - 2 & \text{if } -2 \le x < 2 \\ -x + 6 & \text{if } x \ge 2 \end{cases}

3. Final Answer

The function is defined as:
y={x6if x<23x2if 2x<2x+6if x2y = \begin{cases} x - 6 & \text{if } x < -2 \\ 3x - 2 & \text{if } -2 \le x < 2 \\ -x + 6 & \text{if } x \ge 2 \end{cases}