a) \(x^2=2\Leftrightarrow\left[\begin{array}{nghiempt}x=\sqrt{2}\\x=-\sqrt{2}\end{array}\right.\)\(\Leftrightarrow\left[\begin{array}{nghiempt}1,414\\-1,414\end{array}\right.\)
b) \(x^2=3\Leftrightarrow\left[\begin{array}{nghiempt}x=\sqrt{3}\\x=-\sqrt{3}\end{array}\right.\)\(\Leftrightarrow\left[\begin{array}{nghiempt}x=1,732\\x=-1,732\end{array}\right.\)
c) \(x^2=3,5\Leftrightarrow\left[\begin{array}{nghiempt}x=\sqrt{3,5}\\x=-\sqrt{3,5}\end{array}\right.\)\(\Leftrightarrow\left[\begin{array}{nghiempt}x=1,871\\x=-1,871\end{array}\right.\)
d) \(x^2=4,12\Leftrightarrow\left[\begin{array}{nghiempt}x=\sqrt{4,12}\\x=-\sqrt{4,12}\end{array}\right.\)\(\Leftrightarrow\left[\begin{array}{nghiempt}x=2,030\\x=-0,030\end{array}\right.\)
a) \(x^2=2\)
\(\Rightarrow\begin{cases}x=\sqrt{2}\approx1.414\\x=-\sqrt{2}\approx-1.414\end{cases}\)
b) \(x^2=3\)
\(\Rightarrow\begin{cases}x=\sqrt{3}\approx1.732\\x=-\sqrt{3}\approx-1.732\end{cases}\)
c) \(x^2=3.5\)
\(\Rightarrow\begin{cases}x=\sqrt{3.5}\approx1.871\\x=-\sqrt{3.5}\approx-1.871\end{cases}\)
d) \(x^2=4.12\)
\(\Rightarrow\begin{cases}x=\sqrt{4.12}\approx2.30\\x=-\sqrt{4.12}\approx-2.30\end{cases}\)
Nghiệm của phương trình X2 = a (với a ≥ 0) là căn bậc hai của a.
ĐS. a) x = √2 ≈ 1,414, x = -√2 ≈ -1,414.
b) x = √3 ≈ 1,732, x = -√3 ≈ 1,732.
c) x = √3,5 ≈ 1,871, x = √3,5 ≈ 1,871.
d) x = √4,12 ≈ 2,030, x = √4,12 ≈ 2,030.