`#Hưng`
\(a,3\sqrt{8\sqrt{5}}-2\sqrt{9\sqrt{20}}\\ =\sqrt{9.8\sqrt{5}}-\sqrt{4.9\sqrt{20}}\\ =\sqrt{72\sqrt{5}}-\sqrt{36\sqrt{20}}\\ =\sqrt{\sqrt{5184.5}}-\sqrt{\sqrt{1296.20}}\\ =\sqrt{\sqrt{25920}}-\sqrt{\sqrt{25920}}\\ =0\)
\(b,ĐKXĐ:x\sqrt{x}-\sqrt{x}+x-1\ne0\\ \Rightarrow\sqrt{x}\left(x-1\right)+\left(x-1\right)\ne0\\ \Rightarrow\left(x-1\right)\left(\sqrt{x}+1\right)\ne0\\ \Rightarrow x-1\ne0\left(vì.\sqrt{x}+1>0\right)\\ \Rightarrow x\ne1\)
a , 3 √ 8 √ 5 − 2 √ 9 √ 20 = √ 9.8 √ 5 − √ 4.9 √ 20 = √ 72 √ 5 − √ 36 √ 20 = √ √ 5184.5 − √ √ 1296.20 = √ √ 25920 − √ √ 25920 = 0 b , Đ K X Đ : x √ x − √ x + x − 1 ≠ 0 ⇒ √ x ( x − 1 ) + ( x − 1 ) ≠ 0 ⇒ ( x − 1 ) ( √ x + 1 ) ≠ 0 ⇒ x − 1 ≠ 0 ( v ì . √ x + 1 > 0 ) ⇒ x ≠ 1
