Đáp án:
a)
Ta có
`(x-2)^2 \geq 0`
` => 6(x-2)^2 \geq 0`
` => 6(x-2)^2 +2020 \geq 2020`
b)
Ta có
` (x-1)^2 \geq 0`
` (y-2)^2 \geq 0`
` => 5(x-1)^2 + 6(y-2)^2 + 2020 \geq 2020`
` => B_{min} = 2020; khi ` x= 1; y = 2`
c)
Ta có
` 4(x-1)^2 \geq 0`
` 5(x+y-3)^2 \geq 0`
` => 4(x-1)^2 + 5(x+y-3)^2 +2021 \geq 2021`
`=> C_{min} = 2021;` khi ` x - 1 = 0 => x = 1`
` x + y -3 = 0`
` => -2 + y = 0`
` => y = 2`