Giải sơ qua:
1)\(B=4x^2-4xy+2y^2+1=\left(2x-y\right)^2+y^2+1\ge1\)
2) có vẻ sai đề
B = 4x2 - 4xy + y2 + y2 + 1
= ( 2x - y )2 + y2 + 1
Vì ( 2x - y )2 ≥ 0 , y2 ≥ 0
=> ( 2x - y )2 + y2 ≥ 0 => ( 2x - y )2 + y2 + 1 ≥ 1
Vay minB = 1 <=> 2x - y = 0 -> 2x = y =>x = y = 0