Bài 2: ĐKXĐ: x>=1/4
Ta có: \(\sqrt{4x-1}+\sqrt{9x-\frac94}=15\)
=>\(\sqrt{4\left(x-\frac14\right)}+\sqrt{9\left(x-\frac14\right)}=15\)
=>\(2\cdot\sqrt{x-\frac14}+3\cdot\sqrt{x-\frac14}=15\)
=>\(5\cdot\sqrt{x-\frac14}=15\)
=>\(\sqrt{x-\frac14}=3\)
=>\(x-\frac14=9\)
=>\(x=9+\frac14=9,25\) (nhận)
Bài 1:
\(A=\sqrt{20}-5\cdot\sqrt{\frac15}+\frac{\sqrt5-5}{\sqrt5}-\frac{1}{\sqrt5-2}\)
\(=2\sqrt5-\sqrt5+1-\sqrt5-\frac{1\left(\sqrt5+2\right)}{\left(\sqrt5-2\right)\left(\sqrt5+2\right)}\)
\(=1-\left(\sqrt5+2\right)=1-\sqrt5-2=-\sqrt5-1\)
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