Question

当x、y 取何值时,代数式2x^2+y2-8x+2y+5有最大值,最大值是多少

Answer 1

2x^2+y2-8x+2y+5

=2x^2-8x+8+y^2+2y+1-4

=2(x-2)^2+(y+1)^2-4

当x=2,y=-1时,代数式值最小,最小值为：-4