X^3 + 3X^2 - 18X - 54 = 0
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X^3 + 3X^2 = 18X + 54
X^2 * ( X + 3 ) = 18 * ( X + 3 )
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X^2 = 18
X1 = + V 18 = 3 V 2
X2 = - V 18 = ( - 3 V 2 )
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Ответ: 3 V 2 и ( - 3 V 2 )
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Y = X^4
Y = 2X^2 + 8
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X^4 = 2X^2 + 8
X^2 = A
A^2 - 2A - 8 = 0
D = 4 - 4*1*(-8) = 4 + 32 = 36
V D = 6
X1 = ( 2 + 6) : 2 = 4
X2 = ( - 4) : 2 = ( - 2)
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X^2 = A ---> A > 0
X^2 = 4
X 1= + 2
X2 = - 2
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Y = 2X^2 + 8
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Y1 = 2*4 + 8 = 16
Y2 = 16
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Ответ : ( 2 ; 16 ) и ( - 2 ; 16 )