Answer
The required equation $N(P)=-5P+15000$ number of computers when price per computer is $P$ dollars per computer.
The decrease in number of computer sold is $\Delta N=-500$. Negative sign indicates decrease.
Work Step by Step
Let the required function be $N(P)=m\cdot P+b$. We have $N(1000)=10000$ and $N(1500)=7500$, so, we get $10000=1000m+b$ and $7500=1500m+b$.
Subtract the equations, to get $2500=-500m$, or, $m=-5$.
Substitute the value of $m$ in first equation, to get $10000=-5000+b$, or, $b=15000$.
Therefore, the required equation is $N(P)=-5P+15000$.
Now, the slope of the linear function is $\dfrac{\Delta N}{\Delta P}=-5$. When $\Delta P=100$ dollars, then, $\dfrac{\Delta N}{100}=-5$, or, $\Delta N=-500$, which is the decrease in computers sold. Negative sign indicates decrease.
