Question

Tìm MAx: 

A=-x^2-4x-y^2+2y

B=/x-3/(2-/x-3/)

Answer 1

\(A=-x^2-4x-y^2+2y=-\left(x^2+2\times x\times2+2^2-2^2+y^2-2\times y\times1+1^2-1^2\right)=-\left[\left(x+2\right)^2+\left(y-1\right)^2-5\right]\)

\(\left(x+2\right)^2\ge0\)

\(\left(y-1\right)^2\ge0\)

\(\left(x+2\right)^2+\left(y-1\right)^2-5\ge-5\)

\(-\left[\left(x+2\right)^2+\left(y-1\right)^2-5\right]\le5\)

Vậy Max A = 5 khi x = - 2 và y = 1

Answer 2

\(A=-x^2-4x-y^2+2y\)

\(=-\left(x^2+4x+y^2-2y\right)\)

\(=2y-\left(x+y\right)^2\le2y\)

\(MinA=2y\)

Answer 3

ko có phan b hả bn