Describe and correct the error.

Solve x^3 + 20x = - 2x^3 - 7x

3x^3 + 27x = 0

3x (x^2 + 9) = 0

3x (x-3) (x + 3) = 0

x = { - 3, 0, 3}

Step-by-step explanation:

x² + 9 doesn't factor into (x - 3) (x + 3). That's the factorization for the difference of squares, not a sum of squares.

x² + 9 has only imaginary factors: (x - 3i) (x + 3i).

x = {-3i, 0, 3i}

If x is only real numbers, then x = {0}