Find the value of dy/dx at the given point on the curve.

a. y = 3x² – 4  at the point (1, - 1)

b. y = 4 – 2x² at the point (- 1, 2)

c. y = 2 + 8/x at the point (-2, 2)

d. y = 5x³ – 2x² – 3  at the point (0, - 3)

e. y = x + 5/x at the point (5, 2)

f. y = x- 3/√x at the point (9, 2)