Đáp án:
1/
Ta có
`|x+14| \geq 0`
`|y-7| \geq0`
` => |x+14| + |y-7| + 2020 \geq 2020`
` => B_{Min} = 2020`
Dấu "=" khi ` x + 14 = 0 ; y - 7 = 0`
` => x =-14 ; y = 7`
2/
` A = - |x-10| - |y+20| + 2019`
` = - (|x+10| + |y+20|) + 2019`
Ta có
` |x-10| + |y+20| \geq 0`
` => - (|x-10| + |y+20|) + 2019 \leq 2019`
` => A_{max} = 2019` ; khi
` x -10 = 0; y + 20 = 0`;
` => x = 10; y =-20`