`P = x^2 + 4y^2 - 6x + 4y + 2026`

`P = x^2 - 6x + 9 + 4y^2 + 4y + 1 + 2016`

`P = ( x - 3 )^2 + ( 2y + 1 )^2 + 2016`

`Do  ( x - 3 )^2 >= 0  AA  x`

`( 2y + 1 )^2 >= 0  AA  y`

`P = ( x - 3 )^2 + ( 2y + 1 )^2 + 2016 >= 2016  AA  x ; y`

`Dấu = xảy  ra: {(( x - 3 )^2 = 0 ),(( 2y + 1 )^2 = 0 ):}`

`{( x- 3 = 0 ),( 2y + 1 = 0 ):}`

`{( x = 3 ),( y = -1/2 ):}`

`Vậy   P min = 2016` khi `( x ; y ) = ( 3 ; -1/2 )`