Let the dimensions of the poster be \( l \) (length) and \( w \) (width). We have the following equations based on the problem statement:
- Area: \( l \times w = 10 \) (1)
- Perimeter: \( 2l + 2w = 14 \) (2)
From equation (2), we can simplify it:
\[ l + w = 7 \quad \text{(3)} \]
Now we have a system of equations:
- \( l \times w = 10 \)
- \( l + w = 7 \)
We can solve (3) for \( w \):
\[ w = 7 - l \]
Now substitute this expression for \( w \) into (1):
\[ l \times (7 - l) = 10 \]
Expanding this gives:
\[ 7l - l^2 = 10 \]
Rearranging leads to a quadratic equation:
\[ l^2 - 7l + 10 = 0 \]
We can factor this as:
\[ (l - 5)(l - 2) = 0 \]
This gives us two possible values for \( l \):
\[ l = 5 \quad \text{or} \quad l = 2 \]
Using equation (3) to find the corresponding \( w \):
-
If \( l = 5 \): \[ w = 7 - 5 = 2 \]
-
If \( l = 2 \): \[ w = 7 - 2 = 5 \]
Thus, the dimensions of the poster are:
\[ 5 \text{ feet} \text{ by } 2 \text{ feet} \]
So the final result is:
5 feet by 2 feet.