\(2x+x^2-10\)
\(=x^2+2x-10\)
\(=x^2+2\cdot1\cdot x+1-1+10\)
\(=\left(x+1\right)^2-1+10\)
\(=\left(x+1\right)^2+9\)
Có \(\left(x+1\right)^2\ge0\Rightarrow\left(x+1\right)^2+9\ge9\)
\(\Rightarrow GTLN\left(2x+x^2-10\right)=9\)
với \(\left(x+1\right)^2=0;x=\left(-1\right)\)