Câu 1:
\(a,=3-\left(-2\right)=5\\ b,=5\sqrt{3a}+5\sqrt{3a}-2\sqrt{3a}=8\sqrt{3a}\\ c,=\dfrac{5\sqrt{5}-5+3\sqrt{5}+3}{\left(\sqrt{5}-1\right)\left(\sqrt{5}+1\right)}=\dfrac{8\sqrt{5}-2}{4}=\dfrac{4\sqrt{5}-1}{2}\)
Câu 2:
\(a,P=\dfrac{x+2\sqrt{x}+x-2\sqrt{x}}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}\cdot\dfrac{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}{2\sqrt{x}}\\ P=\dfrac{2x}{2\sqrt{x}}=\sqrt{x}\\ b,P>5\Leftrightarrow\sqrt{x}>5\Leftrightarrow x>25\)
Câu 3:
\(VT=\dfrac{\sqrt{ab}\left(\sqrt{a}+\sqrt{b}\right)}{\sqrt{ab}}\left(\sqrt{a}-\sqrt{b}\right)=\left(\sqrt{a}+\sqrt{b}\right)\left(\sqrt{a}-\sqrt{b}\right)=a-b=VP\)