f(x)=-3(x+4)(x-5)

Solution for f(x)=-3(x+4)(x-5) equation:

Simplifying
f(x) = -3(x + 4)(x + -5)

Multiply f * x
fx = -3(x + 4)(x + -5)

Reorder the terms:
fx = -3(4 + x)(x + -5)

Reorder the terms:
fx = -3(4 + x)(-5 + x)

Multiply (4 + x) * (-5 + x)
fx = -3(4(-5 + x) + x(-5 + x))
fx = -3((-5 * 4 + x * 4) + x(-5 + x))
fx = -3((-20 + 4x) + x(-5 + x))
fx = -3(-20 + 4x + (-5 * x + x * x))
fx = -3(-20 + 4x + (-5x + x2))

Combine like terms: 4x + -5x = -1x
fx = -3(-20 + -1x + x2)
fx = (-20 * -3 + -1x * -3 + x2 * -3)
fx = (60 + 3x + -3x2)

Solving
fx = 60 + 3x + -3x2

Solving for variable 'f'.

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

Divide each side by 'x'.
f = 60x-1 + 3 + -3x

Simplifying
f = 60x-1 + 3 + -3x

Reorder the terms:
f = 3 + 60x-1 + -3x