Question

a. x^2 - 9 = 0                                       b. x^2 + 1 + 0

c.x^2=2                                               d. x^2 - 3 = 0

Answer 1

\(a,\Rightarrow x^2=9\Rightarrow\left[{}\begin{matrix}x=3\\x=-3\end{matrix}\right.\\ b,\Rightarrow x^2=-1\left(vô.lí\right)\Rightarrow x\in\varnothing\\ c,\Rightarrow\left[{}\begin{matrix}x=\sqrt{2}\\x=-\sqrt{2}\end{matrix}\right.\\ d,\Rightarrow x^2=3\Rightarrow\left[{}\begin{matrix}x=\sqrt{3}\\x=-\sqrt{3}\end{matrix}\right.\)

Answer 2

a) \(\Rightarrow\left(x-3\right)\left(x+3\right)=0\)

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

b) \(x^2+1=0\)

\(\Rightarrow x^2=-1\left(VLý.do.x^2\ge0\forall x\right)\)

Vậy \(S=\varnothing\)

c) \(\Rightarrow x=\pm\sqrt{2}\)

d) \(\Rightarrow x^2=3\Rightarrow x=\pm\sqrt{3}\)