Toán Lớp 8: tìm x biết: a) 2018x-1+2019x(1-2018x)=0 b)(x+2)^3-x^2(x-6)-4
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Toán Lớp 8: tìm x biết: a) 2018x-1+2019x(1-2018x)=0 b)(x+2)^3-x^2(x-6)-4
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$\text{ a)}$
$\text{2018x – 1 + 2019x ( 1 – 2018x ) = 0 }$
$\text{⇔ 2018x – 1 = 0 }$
$\text{⇔ 1 – 2019x = 0 }$
$\text{⇒ x = $\frac{1}{2018}$ }$
$\text{⇒ $\frac{1}{2019}$ }$
_____________________________
$\text{b) }$
$\text{( x = 2 )³ – x² ( x – 6 ) – 4 }$
$\text{⇔ x³ + 6x² + 12x + 8 – x³ + 6x² }$
$\text{⇔ 12x² + 12x + 4 = 0 }$
$\text{⇔ 3x² + 3x + 1 }$
$\text{= 0 }$
$\text{suy ra vô nghiệm }$