Explicație pas cu pas:
E(x)=V(x²+4x+4)+V(25y²-20y+4)=>
E(x)=V(x+2)²+V(5y-2)²=>
E(x)=|x+2|+|5y-2| =>E(x)=|5y|+|5y-2|
y€[0,2/5] =>0<=y<=2/5=>0<=5y<=2 =>5y-2<=0
=>E(x)=5y+2-5y=>E(x)=2 =>E(x) const.