Đáp án:
`4) x=2`
`5) x=6`
Giải thích các bước giải:
`4) sqrt(x-2)+2sqrt(x^2-4)=0`
`<=>sqrt(x-2)+2sqrt((x-2)(x+2))=0`
`<=>sqrt(x-2)(1+2sqrt(x+2))=0`
`text{vì}` `2sqrt(x+2)geq0`
`<=>1+2sqrt(x+2)>0`
`text{mà}` `sqrt(x-2)(1+2sqrt(x+2))=0`
`=>sqrt(x-2)=0`
`<=>x-2=0`
`<=>x=2`
`5) sqrt(x-2)+sqrt(4x-8)-1/2sqrt(9x-18)=3`
`<=>sqrt(x-2)+2sqrt(x-2)-3/2sqrt(x-2)=3`
`<=>(1+2-3/2)sqrt(x-2)=3`
`<=>3/2sqrt(x-2)=3`
`<=>sqrt(x-2)=3÷3/2`
`<=>sqrt(x-2)=2`
`<=>x-2=4`
`<=>x=6`
`text{xin 5 sao và hay nhất nha}`
