Question

Cm: -x²+4x-5 <0 với mọi x

Answer 1

Chả hỉu j cả????

Answer 2

\(-x^2+4x-5=-\left(x^2-4x+5\right)=-\left(x^2-4x-4+1\right)=-\left(x^2-4x-4\right)-1=-\left(x-2\right)^2-1\le-1< 0\)