y' = d/dx (9x^2) + d/dx (3x) - d/dx (1) = 18x + 3 - 0 = 18x + 3

y = d/dx (x) + d/dx (3/x) - d/dx (3)
y' = 1 - 3/x^2 - 0 = 1 - 3/x^2

y' = d/dx (x + 3) (x - 3) + (x + 3) d/dx (x - 3)
y' = (1) (x - 3) + (x + 3) (1) = x - 3 + x + 3 = 2x