The initial value of the function \( f(x) = -75x + 1,200 \) is the constant term when \( x = 0 \). In this case, when you purchase the cell phone (which is at \( x = 0 \)), the function evaluates to:
\[ f(0) = -75(0) + 1,200 = 1,200 \]
This means that the value of the cell phone at the time you purchase it is $1,200.
Therefore, the correct interpretation is:
The initial value of 1,200 represents the value of your cell phone at the time you purchase it.