functions whose Wronskian is zero aren't necessarily dependent

Question

The book gave this exapmle to show that the functions whose Wronskian is zero aren't necessarly dependent:$u_{1}(x)=u_{2}(x)=0$ for $x<0$ and $u_{1}(x)=x^{2}, u_{2}(x)=2 x^{2}$ for $x \geq 0$ But what is wrong with their dependence, meanwhile one of them is double of the other one