1 câu trả lời
$\text{3$\sqrt{2x}+$$\dfrac{1}{7}$$\sqrt{98x}-$$\sqrt{72x}+4=0$}$
⇔ $\text{ 3$\sqrt{2x}+$$\dfrac{1}{7}.7\sqrt{2x}-$6$\sqrt{2x}$+4=0}$
⇔$\text{3$\sqrt{2x}+\sqrt{2x}-6\sqrt{2x}+4=0$}$
⇔$\text{4-$2\sqrt{2x}$=0}$
⇔$\text{2(2-$\sqrt{2x})$=0}$
⇔$\text{2-$\sqrt{2x}$=0}$
⇔$\text{$\sqrt{2x}$=2}$
⇔$\text{$(\sqrt{2x}$)²=4}$
⇔$\text{2x=4}$
⇔$\text{x=2}$
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