-x^2+2x-2 =-x^2+2x-1-1 =-(x^2-2x+1)-1 =-(x^2-2.x.1+1^2)-1 =-(x-1)^2-1 Ta có: -(x-1)^2≤0=>-(x-1)^2-1≤-1∀x =>-x^2+2x-2<0∀x in RR Trả lời