To find a model that expresses the revenue $R$ as a function of price $p$, we need to use the relationship:

$R = x \cdot p$

We are also given the demand equation:

$x = -5p + 100$

Now, substitute this expression for $x$ into the revenue equation:

$R = (-5p + 100) \cdot p$

Simplifying this expression:

$R(p) = -5p^2 + 100p$

Thus, the revenue $R$ as a function of $p$ is:

$R(p) = -5p^2 + 100p$

Would you like further details on this?

Here are some related questions to consider:

1. What is the maximum revenue that can be achieved?
2. For what price $p$ will the revenue be maximized?
3. How does the revenue change as the price increases?
4. How does the demand equation relate to real-world sales models?
5. What is the revenue when $p = 10$?

Tip: The maximum revenue can be found by analyzing the vertex of the quadratic function for revenue.