đk x ≥ 0
\(\left(\sqrt{x}\right)^2=\left(\sqrt{7}\right)^2\\ x=7\left(tho\text{a}nm\text{a}n\right)\\ \)
g, đk x ≥ 0
\(\sqrt{x}=\dfrac{1}{3}+3\\ \sqrt{x}=\dfrac{1+3.3}{3}\\ \sqrt{x}=\dfrac{10}{3}\\ \left(\sqrt{x}\right)^2=\left(\dfrac{10}{3}\right)^2\\ x=\dfrac{100}{9}\left(tho\text{a}nm\text{a}n\right)\)