Can someone help me with these please? (Explain 2 and 3 please! And try to do all please!

(note i put the graph in so plz )the graph shows the amount of water that remains in a barrel after it begins to leak. the variable x represents the number of days that have passed since the barrel was filled, and y represents the number of gallons of water that remain in the barrel. what is the slope of the line

Look at the following graph of the given equation. determine whether the equation is a function. explain why or why not.

Simply 8x squared + 5(7x squared- x) - 2x =