Đáp án:
Giải thích các bước giải:
`a) A=sqrt(4+2sqrt(3))+sqrt(4-sqrt(3))`
`A=sqrt(3+2sqrt(3)+1)+sqrt(3-2sqrt(3)+1)`
`A=sqrt((sqrt(3)+1)^2)+sqrt((sqrt(3)-1)^2)`
`A=|sqrt(3)+1|+|sqrt(3)-1|`
`text{vì}` `3>1`
`=>sqrt(3)-1>0`
`=>|sqrt(3)-1|=sqrt(3)-1`
`<=>A=sqrt(3)+1+sqrt(3)-1`
`A=2sqrt(3)`
`b) B=sqrt(6+2sqrt(5))+sqrt(6-2sqrt(5))`
`B=sqrt(5+2sqrt(5)+1)+sqrt(5-2sqrt(5)+1)`
`B=sqrt((sqrt(6)+1)^2)+sqrt((sqrt(6)-1)^2)`
`B=|sqrt(6)+1|+|sqrt(6)-1|`
`text{vì}` `6>1`
`=>sqrt(6)-1>0`
`=>|sqrt(6)-1|=sqrt(6)-1`
`<=>A=sqrt(6)+1+sqrt(6)-1`
`A=2sqrt(6)`
`c) C=sqrt(9x^2)-2x`
`C=|3x|-2x`
`text{vì}` `x<0`
`=>3x<0`
`=>|3x|=-3x`
`<=>C=-3x-2x`
`C=-5x`
`d) D=x-4+sqrt(16-8x+x^2)`
`D=x-4+sqrt((4-x)^2)`
`D=x-4+|4-x|`
`text{vì}` `x>4`
`=>4-x<0`
`=>|4-x|=x-4`
`<=>D=x-4+x-4`
`D=2x-8`
`text{xin 5 sao và hay nhất nha}`
