a: ĐKXĐ: x>=5
\(\sqrt{x-5}+\sqrt{4x-20}+\sqrt{9x-45}=3\)
=>\(\sqrt{x-5}+2\sqrt{x-5}+3\sqrt{x-5}=3\)
=>\(6\sqrt{x-5}=3\)
=>\(\sqrt{x-5}=\frac12\)
=>\(x-5=\frac14\)
=>\(x=5+\frac14=\frac{21}{4}\) (nhận)
b: ĐKXĐ: x>=-1
\(-2\sqrt{x+1}-\sqrt{9x+9}+\frac35\cdot\sqrt{25x+25}=-20\)
=>\(-2\sqrt{x+1}-3\sqrt{x+1}+\frac35\cdot5\sqrt{x+1}=-20\)
=>\(-2\cdot\sqrt{x+1}=-20\)
=>\(\sqrt{x+1}=10\)
=>x+1=100
=>x=99(nhận)
c: ĐKXĐ: x>=2
\(\sqrt{4x-8}-\frac23\cdot\sqrt{36x-72}+\frac54\cdot\sqrt{16x-32}=24\)
=>\(2\sqrt{x-2}-\frac23\cdot6\sqrt{x-2}+\frac54\cdot4\sqrt{x-2}=24\)
=>\(2\sqrt{x-2}-4\cdot\sqrt{x-2}+5\cdot\sqrt{x-2}=24\)
=>\(3\cdot\sqrt{x-2}=24\)
=>\(\sqrt{x-2}=8\)
=>x-2=64
=>x=66(nhận)
d: ĐKXĐ: x<=3
\(2\sqrt{3-x}+\sqrt{12-4x}+\sqrt{75-25x}-\sqrt{3-x}=4\)
=>\(\sqrt{3-x}+2\cdot\sqrt{3-x}+5\cdot\sqrt{3-x}=4\)
=>\(8\cdot\sqrt{3-x}=4\)
=>\(\sqrt{3-x}=\frac12\)
=>\(3-x=\frac14\)
=>\(x=3-\frac14=\frac{11}{4}\) (nhận)
