Ab passes through the points (1,3) and (3,17). if cd is perpendicular to ab, what is the slope of cd?

What is the slope simplify your answer and write it as a proper fraction, improper fraction, or integer

Ascientist wants to use a model to present the results of his detailed scientific investigation. why would a model be useful? a )because the model makes the concepts easier to understand b) because the model is easy to put together and to use c) because the model prevents other scientists from asking questions d) because the model requires the audience to pay full attention to it i don't know what to choose because between a and d a is much more likely than d because it only wants to get the attention of the audience. i'm confuse.

If private savings 'v' = 0.75s and total savings 's' equals $4.20 billion, solve for public and private savings.