Giải phương trình
a) \(\sqrt 2 .x - \sqrt {50}  = 0\);                  
b) \(\sqrt 3 .x + \sqrt 3  = \sqrt {12}  + \sqrt {27}\);
c) \(\sqrt 3 .{x^2} - \sqrt {12}  = 0\);
d) \({{{x^2}} \over {\sqrt 5 }} - \sqrt {20}  = 0\)
Hướng dẫn giải:
a) \(\sqrt{2}.x - \sqrt{50} = 0\)
\(\Leftrightarrow \sqrt{2}x=\sqrt{50}\)
\(\Leftrightarrow x=\frac{\sqrt{50}}{\sqrt{2}}=\sqrt{25}=5\)
b) \(\sqrt{3}.x + \sqrt{3} = \sqrt{12} + \sqrt{27}\)
\(\Leftrightarrow \sqrt{3}(x+1)=2\sqrt{3}+3\sqrt{3}=5\sqrt{3}\)
\(\Leftrightarrow x+1=5\Leftrightarrow x=4\)
c) \(\sqrt{3}x^2-\sqrt{12}=0\)
\(\Leftrightarrow \sqrt{3}x^2=2\sqrt{3}\)
\(\Leftrightarrow x^2=2\)
\(\Leftrightarrow x=\pm 2\)
d) \(\frac{x^{2}}{\sqrt{5}}- \sqrt{20} = 0\)
\(\Leftrightarrow \frac{x^2}{\sqrt{5}}=\sqrt{20}\)
\(\Leftrightarrow x^2=\sqrt{20.5}=10\)
\(\Leftrightarrow x=\pm \sqrt{10}\)