\(x^2-3=\left(x-\sqrt{3}\right)\left(x+\sqrt{3}\right)\)
\(x^2-6=\left(x-\sqrt{6}\right)\left(x+\sqrt{6}\right)\)
\(x^2+2\sqrt{3}x+3=x^2+2\sqrt{3}.x+\sqrt{3}^2=\left(x+\sqrt{3}\right)^2\)
\(x^2-2\sqrt{5}x+5=x^2-2\sqrt{5}x+\sqrt{5}^2=\left(x-\sqrt{5}\right)^2\)