[tex]a)~x^2=8 \Leftrightarrow x^2-8=0 \Leftrightarrow (x+2 \sqrt{2})(x - 2\sqrt{2} )=0 \Rightarrow x= \pm 2 \sqrt{2}. \\ \\ b)~ \sqrt{x}=16 \Rightarrow x=16^2= 256. \\ \\ c)~5=x^2 \Leftrightarrow 5-x^2=0 \Leftrightarrow ( \sqrt{5}+x)( \sqrt{5}-x)=0 \Rightarrow x= \pm \sqrt{5}. \\ \\ d)~ \sqrt{x}=9 \Rightarrow x=9^2=81. [/tex]
