( 3X + 1)*( X - 4 ) = 3X^2 - 12X + X - 4 = 3X^2 - 11X - 4
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6X^2 + 7X - 3 + 3X^2 - 11X - 4 = 9X^2 - 4X - 7
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9X^2 - 6X - 8 = 9X^2 - 4X - 7
9X^2 - 9X^2 - 6X + 4X - 8 + 7 = 0
- 2X - 1 = 0
2X = - 1
X = ( - 0.5 )
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Ответ Х = ( - 0.5 )