Đáp án+Giải thích các bước giải:
`\sqrt{5x-6}=x-3(x>=3)`
`<=>5x-6=(x-3)^2`
`<=>5x-6=x^2-6x+9`
`<=>x^2-6x-5x+9+6=0`
`<=>x^2-11x+15=0`
`<=>x^2-2.x. 11/2+121/4-61/4=0`
`<=>(x-11/2)^2-(\frac{\sqrt{61}}{2})^2=0`
`<=>(x-11/2-\frac{\sqrt{61}}{2})(x-11/2+\frac{\sqrt{61}}{2})=0`
`<=>(x-\frac{\sqrt{61}+11}{2})(x+\frac{\sqrt{61}-11}{2})=0`
`<=>[(x=\frac{\sqrt{61}+11}{2}(tm)),(x=\frac{-\sqrt{61}+11}{2}(ktm)):}`
Vậy `S={\frac{\sqrt{61}+11}{2}}`
