x2 - 9 = 0
x2 = 9
x = 3 ( vì 32 = 9)
x2 - 16 = 0
x2 = 16
x = 4 ( vì 42 = 16)
1. X^2 - 9 = 0
x^2 = 0 + 9
x^2 = 9
x^2 = 3^2
=> x = 3
2. x^2 = 0 + 9
x^2 = 9
x^2 = 3^2
=> x = 3
3. x^2 = 9
x^2 = 3^2
=> x = 3
4. x^2 - 16 = 0
x^2 = 0 + 16
x^2 = 16
x^2 = 4^2
=> x = 4
\(x^2-9=0\)
\(\Leftrightarrow x^2=0+9\)
\(\Leftrightarrow x^2=9\)
\(\Leftrightarrow x=\sqrt{9}\)
\(\Leftrightarrow\orbr{\begin{cases}x=\sqrt{3^2}\\x=\sqrt{\left(-3\right)^2}\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=3\\x=-3\end{cases}}\)
Vậy \(x=\pm3\)
\(x^2-9=0\)
\(\Rightarrow x^2=9\)
\(\Rightarrow x=\pm3\)
2 câu tiếp theo tương khác
\(x^2-16=0\)
\(\Rightarrow x^2=16\)
\(\Rightarrow x=\pm4\)
