A triangle has side lengths measuring [tex]$2x + 2 \, \text{ft}$[/tex], [tex]$x + 3 \, \text{ft}$[/tex], and [tex]n \, \text{ft}$[/tex].

Which expression represents the possible values of [tex]n[/tex], in feet? Express your answer in simplest terms.

A. [tex]x - 1 \ \textless \ n \ \textless \ 3x + 5[/tex]

B. [tex]n = 3x + 5[/tex]

C. [tex]n = x - 1[/tex]

D. [tex]3x + 5 \ \textless \ n \ \textless \ x - 1[/tex]



Answer :

To determine which expression represents the possible values of [tex]\( n \)[/tex] that form a valid triangle with sides [tex]\( 2x + 2 \)[/tex], [tex]\( x + 3 \)[/tex], and [tex]\( n \)[/tex] (all in feet), we must use the triangle inequality theorem. This theorem states that the sum of the lengths of any two sides of a triangle must be greater than the length of the third side.

Let's denote the sides of the triangle as follows:
- Side 1: [tex]\( a = 2x + 2 \)[/tex]
- Side 2: [tex]\( b = x + 3 \)[/tex]
- Side 3: [tex]\( c = n \)[/tex]

We will apply the triangle inequality theorem to obtain the possible values for [tex]\( n \)[/tex].

### Step 1: Apply the Inequality [tex]\( a + b > c \)[/tex]

[tex]\[ (2x + 2) + (x + 3) > n \][/tex]

Simplify:

[tex]\[ 3x + 5 > n \][/tex]

Thus:

[tex]\[ n < 3x + 5 \][/tex]

### Step 2: Apply the Inequality [tex]\( a + c > b \)[/tex]

[tex]\[ (2x + 2) + n > (x + 3) \][/tex]

Simplify:

[tex]\[ 2x + 2 + n > x + 3 \][/tex]

Subtract [tex]\( x \)[/tex] from both sides:

[tex]\[ x + 2 + n > 3 \][/tex]

Subtract 2 from both sides:

[tex]\[ x + n > 1 \][/tex]

Therefore:

[tex]\[ n > 1 - x \][/tex]

Since [tex]\( x + n > 1 \)[/tex] is valid in all cases where [tex]\( n > x - 1 \)[/tex], we derive:

[tex]\[ n > x - 1 \][/tex]

### Step 3: Apply the Inequality [tex]\( b + c > a \)[/tex]

[tex]\[ (x + 3) + n > (2x + 2) \][/tex]

Simplify:

[tex]\[ x + 3 + n > 2x + 2 \][/tex]

Subtract [tex]\( x \)[/tex] from both sides:

[tex]\[ 3 + n > x + 2 \][/tex]

Subtract 2 from both sides:

[tex]\[ n > x - 1 \][/tex]

Thus, the same inequality is confirmed:

[tex]\[ n > x - 1 \][/tex]

### Conclusion

Combining the results of all three inequalities, we have:

[tex]\[ x - 1 < n < 3x + 5 \][/tex]

This can be written in interval notation:

[tex]\[ n \in (x - 1, 3x + 5) \][/tex]

Therefore, the expression that correctly represents the possible values of [tex]\( n \)[/tex] for the triangle is:

[tex]\[ x - 1 < n < 3x + 5 \][/tex]