Given the trapezoid ABCD, find the length of AB

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.

The sum of these consecutive integers is equal to 9 less than 4 times the least of the integer. find the three integers

State one method by which you can recognize a perfect square trinomial.