How do you do this problems?

If x=-3 is the only x-intercept of the graph of a quadratic equation, which statement best discribes the discriminant of the equation?

An architect is designing a water fountain for a park she uses the given function to model the water jet flowing from the fountain nozzles where h(x) gives the height of the water jugs in feet x feet from the starting point h(x)=-1/20x+x+15

Line l passes through points (0,4) and (3,6) what is the slope of a line that is parallel to line l -2/3 -3/2 2/3 3/2