f(x) = (x - (2 + i))(x - (2 - i))(x - 5)
f(x) = (x - 2 - i)(x - 2 + i)(x - 5)
f(x) = (x(x - 2 + i) - 2(x - 2 + i) - i(x - 2 + i))(x - 5)
f(x) = ((x2 - 2x + ix - 2x + 4 - 2i - ix + 2i - i2)(x - 5)
f(x) = (x2 - 4x + 4 + 1)(x - 5)
f(x) = (x2 - 4x + 5)(x - 5)
f(x) = x(x2 - 4x + 5) - 5(x2 - 4x + 5)
f(x) = x3 - 4x2 + 5x - 5x2 + 20x - 25
f(x) = x3 - 9x2 + 25x - 25