Passes through (2, 3) and has slope of - 1/2

Which expression is equivalent to 2x^2+2x-4/2x^2-4x+2

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.

See attachment below and find the equivalent of tan(∠qsr)