We have the following:
The intersection with the x-axis is when the value of y is 0, that is, the computer already has a value of 0 and has no commercial value.
we found it like this
[tex]\begin{gathered} 0=-400x+4000 \\ 400x=4000 \\ x=\frac{4000}{400} \\ x=10 \end{gathered}[/tex]which means that in 10 years, the computer does not represent a commercial value
to calculate the number of years that have passed when the computer has a value of 2000, y = 2000, therefore we replace
[tex]\begin{gathered} 2000=-400x+4000 \\ 400x=4000-2000 \\ x=\frac{2000}{400} \\ x=5 \end{gathered}[/tex]This means that in a total of 5 years the value of the computer will be $ 2000
