Let F(x, y, λ) = xy+λ (x+y-2)
F'x=y+λ=0
F'y=x+λ=0
F'λ=x+y-2=0
X=y= 1,λ =- 1。
So z = xy max =/kloc-0 /×1=1.
6.∫∫D dσ means integral area =πr? =4π
∫D dσ=∫(0,2π) dθ∫(0,2) rdr
=2π∫(0,2) rdr
=πr? |(0,2)=4π