+128474 (x + 4) ( x + 2) (2x+ 1) (x - 2) = 0
(x^2 - 4) ( x + 4) (2x + 1) = 0
(x^2 - 4) (2x^2 + 9x + 4) = 0
2x^4 + 9x^3 + 4x^2
-8x^2 - 36x - 16
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2x^4 + 9x^3 - 4x^2 - 36x - 16 = 0
The error was made in multiplying (x + 4) (2x + 1). The first term is 2x^2, not x^2.
