To solve for the width of the trampoline using the equation \( w^2 + 6w - 112 = 0 \), we can use the quadratic formula:
\[
w = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
\]
In our equation, the coefficients are:
- \( a = 1 \)
- \( b = 6 \)
- \( c = -112 \)
Now, substitute these values into the quadratic formula:
- Compute the discriminant:
\[
b^2 - 4ac = 6^2 - 4 \cdot 1 \cdot (-112)
\]
\[
= 36 + 448
\]
\[
= 484
\]
- Find the square root of the discriminant:
\[
\sqrt{484} = 22
\]
- Now, substitute back into the quadratic formula:
\[
w = \frac{-6 \pm 22}{2 \cdot 1}
\]
This gives us two potential solutions:
\[
w = \frac{-6 + 22}{2} = \frac{16}{2} = 8
\]
\[
w = \frac{-6 - 22}{2} = \frac{-28}{2} = -14
\]
Since width cannot be negative, we discard \( w = -14 \).
Thus, the width of the trampoline is
\[
\boxed{8} \text{ ft.}
\]
To confirm, we can also find the length:
\[
l = w + 6 = 8 + 6 = 14 \text{ ft.}
\]
Finally, check the area:
\[
\text{Area} = w \times l = 8 \times 14 = 112 \text{ ft}^2,
\]
which matches the given area of the trampoline. Therefore, the width is indeed
\[
\boxed{8} \text{ ft.}
\]