Ta có: D = x2 +100x - 1000
= x2 +100x +2500 - 3500
= ( x + 50)2 -3500
Vì : \(\left(x+50\right)^2\ge0\forall x\)
\(\Rightarrow\left(x+50\right)^2-3500\ge-3500\forall x\)
Hay : \(D\ge-3500\forall x\)
Vậy: Min D = -3500 tại \(\left(x+50\right)^2=0\Rightarrow x=-50\)
=.= hk tốt!!