Find all the solutions to 3 x cubed minus 6 x squared plus 30 x minus 20 is equal to negative 20

Add 20 to both sides to get 3x³ − 6x² + 30x = 0, then factor: 3x(x² − 2x + 10) = 0. This gives x = 0, or x² − 2x + 10 = 0. Using the quadratic formula, the latter roots are (2 ± √(4 − 40))/2 = 1 ± 3i, so the solutions are 0, 1 + 3i, and 1 − 3i. This matches choice D.

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