`\sqrt{4x+20}-3\sqrt{5+x}+4/3\sqrt{9x+45}=9(x>=-5)`
`<=>2\sqrt{x+5}-3\sqrt{x+5}+4/3 .3\sqrt{x+5}=9`
`<=>2\sqrt{x+5]-3\sqrt{x+5}+4\sqrt{x+5}=9`
`<=>3\sqrt{x+5}=9`
`<=>\sqrt{x+5}=3`
`<=>x+5=9`
`<=>x=4(tm)`
Vậy `S={4}`
`\sqrt{25x-25}-15/2\sqrt{\frac{x-1}{9}}=6+\sqrt{x-1}(x>=1)`
`<=>5\sqrt{x-1}-15/2 .1/3 \sqrt{x-1}-\sqrt{x-1]=6`
`<=>5\sqrt{x-1}-5/2\sqrt{x-1}-\sqrt{x-1}=6`
`<=>\sqrt{x-1}(5-5/2-1)=6`
`<=>3/2\sqrt{x-1}=6`
`<=>\sqrt{x-1}=4`
`<=>x-1=16`
`<=>x=17(tm)`
Vậy `S={17}`
