What’s the sales tax rate? please help me. I’ve very confused

The parabola y = x² - 4 opens: a.) up b.) down c.) right d.) left

Lindsay used two points, (x,y; ) and (+2.82), to find the equation of the line, y = mx + b, that passes through the points. y2-y, first, she used the definition of slope and determined that the value of mis x, - . given this information, which expression must represent the value of b?

Answer! if you don’t mind, can you explain