Write the expanded exponential form of the number 1287.5478​

We just started the introduction into circles and i have no idea how to do this.

Every weekday, mr. jones bikes from his home to his job. sometimes he rides along two roads, the long route that is shown by the solid lines. other times, he takes the shortcut shown by the dashed line. how many fewer kilometers does mr. jones bike when he takes the shortcut instead of the long route?

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