11. Let [tex]$R = \{(x, y): y \leq x + 2, y \geq 2 - x, \text{ and } y \geq 0\}$[/tex]. Find the domain and range.



Answer :

To determine the domain and range of the region [tex]\( R = \{(x, y): y \leq x+2, y \geq 2-x, \text{ and } y \geq 0\} \)[/tex], we need to analyze the given inequalities step by step and understand how they intersect.

### Step 1: Analyzing the Inequalities

We are given three inequalities:

1. [tex]\( y \leq x + 2 \)[/tex]
2. [tex]\( y \geq 2 - x \)[/tex]
3. [tex]\( y \geq 0 \)[/tex]

### Step 2: Finding the Intersections

Let's find the points of intersection of these lines, as these will form the vertices of the region [tex]\( R \)[/tex].

#### Intersection of [tex]\( y = x + 2 \)[/tex] and [tex]\( y = 2 - x \)[/tex]:

Set [tex]\( x + 2 = 2 - x \)[/tex]:

[tex]\[ x + 2 = 2 - x \][/tex]
[tex]\[ 2x = 0 \][/tex]
[tex]\[ x = 0 \][/tex]

So, substituting [tex]\( x = 0 \)[/tex] back into either equation gives:

[tex]\[ y = x + 2 = 0 + 2 = 2 \][/tex]

Therefore, one point of intersection is [tex]\((0, 2)\)[/tex].

#### Intersection of [tex]\( y = x + 2 \)[/tex] and [tex]\( y = 0 \)[/tex]:

Set [tex]\( x + 2 = 0 \)[/tex]:

[tex]\[ y = x + 2 \][/tex]
[tex]\[ 0 = x + 2 \][/tex]
[tex]\[ x = -2 \][/tex]

So, substituting [tex]\( x = -2 \)[/tex] back into the equation gives:

[tex]\[ y = 0 \][/tex]

Therefore, another point of intersection is [tex]\((-2, 0)\)[/tex].

#### Intersection of [tex]\( y = 2 - x \)[/tex] and [tex]\( y = 0 \)[/tex]:

Set [tex]\( 2 - x = 0 \)[/tex]:

[tex]\[ y = 2 - x \][/tex]
[tex]\[ 0 = 2 - x \][/tex]
[tex]\[ x = 2 \][/tex]

So, substituting [tex]\( x = 2 \)[/tex] back into the equation gives:

[tex]\[ y = 0 \][/tex]

Therefore, the third point of intersection is [tex]\((2, 0)\)[/tex].

### Step 3: Determining the Domain and Range

From the points of intersection, we know the vertices of the triangular region defined by these inequalities are [tex]\((0, 2)\)[/tex], [tex]\((-2, 0)\)[/tex], and [tex]\((2, 0)\)[/tex].

Domain:

The domain is all [tex]\( x \)[/tex]-values that are part of the region [tex]\( R \)[/tex].

Examining the [tex]\( x \)[/tex]-coordinates of the vertices:

- Lowest [tex]\( x \)[/tex]-value is [tex]\(-2\)[/tex]
- Highest [tex]\( x \)[/tex]-value is [tex]\(2\)[/tex]

So, the domain is:

[tex]\[ [-2, 2] \][/tex]

Range:

The range is all [tex]\( y \)[/tex]-values that are part of the region [tex]\( R \)[/tex].

Examining the [tex]\( y \)[/tex]-coordinates of the vertices and how [tex]\( y \)[/tex] varies within the region:

- Lowest [tex]\( y \)[/tex]-value is [tex]\(0\)[/tex]
- Highest [tex]\( y \)[/tex]-value is [tex]\(2\)[/tex]

So, the range is:

[tex]\[ [0, 2] \][/tex]

### Answer

The domain and range of the region [tex]\( R \)[/tex] are:

- Domain: [tex]\([-2, 2]\)[/tex]
- Range: [tex]\([0, 2]\)[/tex]