900x+100x=10 x8+x(4+2)=0 tìm x

900x + 100x = 10

<=>1000x – 10 =0

<=> 10 ( 100x – 1) =0

<=> 100x – 1 =0

<=> 100x = 1

<=> x = 1/100

Vậy S={1/100}

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x8 + x(4x+2)=0

<=> 8x + 4x^2 + 2x =0

<=>4x^2 + 10x = 0

<=> 2x(2x + 5)=0

<=>\(\left[ \begin{array}{l}2x=0\\2x+5=0\end{array} \right.\) <=>\(\left[ \begin{array}{l}x=0\\x=\frac{-5}{2}\end{array} \right.\)  

Vậy S={0;-5/2}

$\color{lightblue}{eriet}$