k(x)=3(x-1)(x+1)

Solution for k(x)=3(x-1)(x+1) equation:

Simplifying
k(x) = 3(x + -1)(x + 1)

Multiply k * x
kx = 3(x + -1)(x + 1)

Reorder the terms:
kx = 3(-1 + x)(x + 1)

Reorder the terms:
kx = 3(-1 + x)(1 + x)

Multiply (-1 + x) * (1 + x)
kx = 3(-1(1 + x) + x(1 + x))
kx = 3((1 * -1 + x * -1) + x(1 + x))
kx = 3((-1 + -1x) + x(1 + x))
kx = 3(-1 + -1x + (1 * x + x * x))
kx = 3(-1 + -1x + (1x + x2))

Combine like terms: -1x + 1x = 0
kx = 3(-1 + 0 + x2)
kx = 3(-1 + x2)
kx = (-1 * 3 + x2 * 3)
kx = (-3 + 3x2)

Solving
kx = -3 + 3x2

Solving for variable 'k'.

Move all terms containing k to the left, all other terms to the right.

Divide each side by 'x'.
k = -3x-1 + 3x

Simplifying
k = -3x-1 + 3x