`C = -1/4x^2 + x - 2 = -1/4x^2 + x - 1 - 1 = -(1/2 - 1)^2 - 1 < 0 ∀ x`
`D = -3x^2 - 6x - 9 = -3x^2 - 6x - 3 - 6 = -3(x - 1)^2 - 6 < 0 ∀ x`
`E = (1 - 2x)(x - 1) = x - 1 - 2x^2 + 2x = -2x^2 + x - 1`
`= -2x^2 + x - 1/8 - 9/8 = -(x√2 - 1/(√8))^2 - 9/8 < 0 ∀ x`
`F = -x^2 - y^2 + 2x - 2y - 3 = (-x^2 + 2x -1) + (-y^2 - 2y - 1) - 1`
`= -(x - 1)^2 - (y + 1)^2 - 1 < 0 ∀ x`