Now y = 3x − x³

and so

Since y = 3x − x³ then when x = 2, y = -2.

So we need the equation of the line passing through (2,-2) with slope -9.

Using y - y₁ = m(x - x₁), we have:

y + 2 = -9(x - 2)

So the required equation is:

y = -9x + 16

Or, in general form: 9x + y - 16 = 0.