题目计算:(1)12+8−53+2(1)\sqrt{12}+\sqrt{8}-5\sqrt{3}+\sqrt{2}(1)12+8−53+2.(2)(5+2)(5−2)+(−3)2(2)(\sqrt{5}+\sqrt{2})(\sqrt{5}-\sqrt{2})+\sqrt{{(-3)}^{2}}(2)(5+2)(5−2)+(−3)2.(3)(3)(3)已知a=5+1a=\sqrt{5}+1a=5+1,求代数式a2−2a+7a^{2}-2a+7a2−2a+7的值.知识点：绝对值的性质;算术平方根;估算无理数的大小;实数的运算章节：未标注
