Find all the solutions to the equation 4 x cubed plus 16 x squared plus 28 x is equal to 0

Factor the equation as 4x(x² + 4x + 7) = 0, so one solution is x = 0. For the quadratic, the quadratic formula gives x = (-4 ± √(16 − 28))/2 = -2 ± i√3, so the solutions are 0, -2 + i√3, and -2 − i√3. This matches choice D.

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