Ai giúp em với ạ Cả 3 bài

\[\begin{array}{l} 1a)\,\,A = \sqrt {4 + \sqrt {10 + 2\sqrt 5 } } + \sqrt {4 - \sqrt {10 + 2\sqrt 5 } } \\ \Rightarrow {A^2} = 4 + \sqrt {10 + 2\sqrt 5 } + 2\sqrt {\left( {4 + \sqrt {10 + 2\sqrt 5 } } \right)\left( {4 - \sqrt {10 + 2\sqrt 5 } } \right)} + 4 - \sqrt {10 + 2\sqrt 5 } \\ = 8 + 2\sqrt {16 - 10 - 2\sqrt 5 } \\ = 8 + 2\sqrt {6 - 2\sqrt 5 } \\ = 8 + 2\sqrt {{{\left( {\sqrt 5 - 1} \right)}^2}} \\ = 8 + 2\left| {\sqrt 5 - 1} \right|\\ = 8 + 2\sqrt 5 - 2\,\,\,\,\left( {do\,\,\,\sqrt 5 - 1 > 0} \right)\\ = 6 + 2\sqrt 5 .\\ \Rightarrow A = \sqrt {6 + 2\sqrt 5 } = \sqrt {{{\left( {\sqrt 5 + 1} \right)}^2}} = \left| {\sqrt 5 + 1} \right| = \sqrt 5 + 1.\\ b)\,\,\,E\,\,lam\,\,tuong\,\,tu\,\,\,cau\,\,tren.\\ 2\,\,a)\,\,\,\,A = \sqrt {6 + 2\sqrt {6 - 2\sqrt {4 + 2\sqrt 3 } } } \\ = \sqrt {6 + 2\sqrt {6 - 2\sqrt {{{\left( {\sqrt 3 + 1} \right)}^2}} } } = \sqrt {6 + 2\sqrt {6 - 2\left| {\sqrt 3 + 1} \right|} } \\ = \sqrt {6 + 2\sqrt {6 - 2\sqrt 3 - 2} } = \sqrt {6 + 2\sqrt {4 - 2\sqrt 3 } } = \sqrt {6 + 2\sqrt {{{\left( {\sqrt 3 - 1} \right)}^2}} } \\ = \sqrt {6 + 2\left| {\sqrt 3 - 1} \right|} = \sqrt {6 + 2\sqrt 3 - 2} \,\,\,\,\left( {do\,\,\,\sqrt 3 - 1 > 0} \right)\\ = \sqrt {4 + 2\sqrt 3 } = \sqrt {{{\left( {\sqrt 3 + 1} \right)}^2}} = \left| {\sqrt 3 + 1} \right| = \sqrt 3 + 1.\\ b)\,\,Cau\,\,b\,\,em\,\,lam\,\,\,tuong\,\,tu.\\ 3)\,a)\,\,\sqrt {10 - x} + \sqrt {x + 3} = 5\\ DK:\,\,\, - 3 \le x \le 10\\ \Rightarrow Pt \Leftrightarrow {\left( {\sqrt {10 - x} + \sqrt {x + 3} } \right)^2} = 25\\ \Leftrightarrow 10 - x + 2\sqrt {\left( {10 - x} \right)\left( {x + 3} \right)} + x + 3 = 25\\ \Leftrightarrow 2\sqrt {\left( {10 - x} \right)\left( {x + 3} \right)} = 12\\ \Leftrightarrow \sqrt {\left( {10 - x} \right)\left( {x + 3} \right)} = 6\\ \Leftrightarrow \left( {10 - x} \right)\left( {x + 3} \right) = 36\\ \Leftrightarrow 10x + 30 - {x^2} - 3x = 36\\ \Leftrightarrow {x^2} - 7x + 6 = 0\\ \Leftrightarrow \left( {x - 1} \right)\left( {x - 6} \right) = 0\\ \Leftrightarrow \left[ \begin{array}{l} x = 1\,\,\,\left( {tm} \right)\\ x = 6\,\,\,\left( {tm} \right) \end{array} \right.. \end{array}\] Các câu sau em làm tương tự nhé em.