Question

cmr 

giups minh :((

Answer 1

\(-x^2+4x-10\)

\(=-\left(x^2-4x+10\right)\)

\(=-\left(x^2-4x+4+6\right)\)

\(=-\left(x-2\right)^2-6< 0\forall x\)

Answer 2

\(4x-10-x^2\\ =-\left(x^2-4x+4\right)-6\\ =-\left(x-2\right)^2-6\)

Nhận xét: 

\(\left(x-2\right)^2\ge0\\ \Rightarrow-\left(x-2\right)^2\le0\\ \Rightarrow-\left(x-2\right)^2-6\le-6< 0\left(đpcm\right)\)