Bài 1:
a: \(\sqrt{12}-\sqrt3=2\sqrt3-\sqrt3=\sqrt3\)
b: \(-2\sqrt{20}+6\sqrt5=-2\cdot2\sqrt5+6\sqrt5=-4\sqrt5+6\sqrt5=2\sqrt5\)
c: \(\sqrt{8-2\sqrt{15}}-\sqrt5\)
\(=\sqrt{\left(\sqrt5-\sqrt3\right)^2}-\sqrt5\)
\(=\sqrt5-\sqrt3-\sqrt5=-\sqrt3\)
d: \(\left(\sqrt2+\sqrt5\right)^2=2+2\cdot\sqrt2\cdot\sqrt5+5=7+2\sqrt{10}\)
e: \(\left(\sqrt5-2\right)\left(\sqrt5+2\right)=5-4=1\)
Bài 2:
a: \(\sqrt3\cdot x-\sqrt{12}=0\)
=>\(x\cdot\sqrt3=\sqrt{12}=2\sqrt3\)
=>x=2
b: \(x\cdot\sqrt2+\sqrt2=\sqrt8+\sqrt{18}\)
=>\(x\cdot\sqrt2=2\sqrt2+3\sqrt2-\sqrt2=4\sqrt2\)
=>x=4
c: \(\sqrt5\cdot x^2-\sqrt{20}=0\)
=>\(x^2\cdot\sqrt5=2\sqrt5\)
=>\(x^2=2\)
=>\(x=\pm\sqrt2\)
