Question

Đưa thừa số ra ngoài dấu căn*

\(\sqrt{20}\)=.....................

\(\sqrt{18x^2}\)=.................(với x ≥ 0)

\(\sqrt{18x^2}\)=..................(với x < 0)

Answer 1

\(\sqrt{20}=\sqrt{4.5}=\sqrt{4}.\sqrt{5}=2\sqrt{5}\\ \sqrt{18x^2} =\sqrt{2.9x^2}=\sqrt{9x^2}.\sqrt{2}=\sqrt{\left(3x\right)^2}.\sqrt{2}\\ =\left|3x\right|\sqrt{2}=3x\sqrt{2}\left(vì.x\ge0\right)\\ \sqrt{18x^2}=\sqrt{2.9x^2}=\sqrt{9x^2}.\sqrt{2}=\sqrt{\left(3x\right)^2}.\sqrt{2}\\ =\left|3x\right|\sqrt{2}=-3x\sqrt{2}\left(vì.x< 0\right)\)

Answer 2

\(\sqrt{20}=\sqrt{2^2.5}=2\sqrt{5}\\ \sqrt{18x^2}=\sqrt{3^2.2.x^2}=3.\left|x\right|.\sqrt{2}=3x\sqrt{2}\left(vìx\ge0\right)\\ \sqrt{18x^2}=\sqrt{3^2.2.x^2}=3.\left|x\right|.\sqrt{2}=-3x\sqrt{2}\left(vìx< 0\right)\)