Let:
P = Profit
n = Number of increments by $1
R = Revenue
The profit is given by:
[tex]\begin{gathered} P=10+1n \\ P=10+n \end{gathered}[/tex]Therefore, the revenue is:
[tex]R=(10+n)(1000-100n)[/tex]Expand the equation using the distributive property:
[tex]\begin{gathered} R=10000-1000n+1000n-100n^2 \\ R=-100n^2+10000 \end{gathered}[/tex]The maximum profit of this quadratic function is located at the vertex, we can find the vertex as follows:
[tex]\begin{gathered} V(h,k) \\ h=-\frac{b}{2a} \\ a=-100 \\ b=0 \\ k=R(h)=R(0)=10000 \end{gathered}[/tex]The vertex is (0,10000) in another words the maximum profit is achieve if you don't raise the price.