Accounting please please help and thank you

There were 816 people at a concert when a band started to play. after each song, only half the people stayed to hear the next song. how many people were left at the concert after x songs? write a function to represent this scenario.

Which is the graph of f(x) = (4)x? image for option 1 image for option 2 image for option 3 image for option 4

In which form is the following function written? y = - 2(x – 3)(x + 5)