a) \(x^2=15\)

\(\Rightarrow\left[{}\begin{matrix}x=\sqrt{15}\\x=-\sqrt{15}\end{matrix}\right.\)

b) \(x^2=22,8\)

\(\Rightarrow\left[{}\begin{matrix}x=\sqrt{22,8}\\x=-\sqrt{22,8}\end{matrix}\right.\)

c) \(x^2=351\)

\(\Rightarrow\left[{}\begin{matrix}x=\sqrt{351}=3\sqrt{39}\\x=-\sqrt{351}=-3\sqrt{39}\end{matrix}\right.\)

d) \(x^2=0,46\)

\(\Rightarrow\left[{}\begin{matrix}x=\sqrt{0,46}\\x=-\sqrt{0,46}\end{matrix}\right.\)

a) x=\(\sqrt{15}\)

_{b) X=\(\sqrt{22.8}\)}

c) x=\(\sqrt{351}\)

d) x=\(\sqrt{0.46}\)

x 2  = 15 ⇒  x 1 = 15  ≈ 3,873

x 2 = - 15  ≈ -3,873

x 2  = 22,8 ⇒ x 1 = 22 , 8 ≈ 4,7749

x 2 = - 22 , 8  ≈ -4,7749

x 2 = 351 ⇒ x 1 = 351 ≈ 18,785

x 2 = - 351 ≈ -18,785

x 2   =   0 , 3982   ⇔   x   =   ± √ 0 , 3982

Ta có: 0,3982 = 39,82:100

Do đó: √0,3982 = √39,82 : √100 = 6,310 : 10 = 0,631

Vậy x = ±0,631