f(x)=(x-6)(x+3)

Solution for f(x)=(x-6)(x+3) equation:

Simplifying
f(x) = (x + -6)(x + 3)

Multiply f * x
fx = (x + -6)(x + 3)

Reorder the terms:
fx = (-6 + x)(x + 3)

Reorder the terms:
fx = (-6 + x)(3 + x)

Multiply (-6 + x) * (3 + x)
fx = (-6(3 + x) + x(3 + x))
fx = ((3 * -6 + x * -6) + x(3 + x))
fx = ((-18 + -6x) + x(3 + x))
fx = (-18 + -6x + (3 * x + x * x))
fx = (-18 + -6x + (3x + x2))

Combine like terms: -6x + 3x = -3x
fx = (-18 + -3x + x2)

Solving
fx = -18 + -3x + x2

Solving for variable 'f'.

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

Divide each side by 'x'.
f = -18x-1 + -3 + x

Simplifying
f = -18x-1 + -3 + x

Reorder the terms:
f = -3 + -18x-1 + x