Đáp án:
`E=6-2x-sqrt{9-6x+x^2}(x<3)` $\\$ `=6-2x-sqrt{(x-3)^2}` $\\$ `=6-2x-|x-3|` $\\$ `=6-2x-(3-x)=6-2x-3+x` $\\$ `=3-x` $\\$ `F=\sqrt{x^2-2x+1}/(2-2x)=\sqrt{(x-1)^2}/(2-2x)` $\\$ `=|x-1|/(2-2x)` $\\$ `G=\sqrt{9x^4+6x^2+1}-3x^2=\sqrt{(3x^2+1)^2}-3x^2` $\\$ `=3x^2+1-3x^2=1` $\\$ `H=\sqrt{b^2-b+1/4}-2b+1/2=\sqrt{(b-1/2)^2}-2b` $\\$ `=|b-1/2|-2b+1/2` $\\$ `=b-1/2-2b+1/2(do \ b>=1/2)=-b`
