Let $$H = \mathrm{span} \left\lbrace \left<-1,2,-1,-1\right>, \left<-2,4,-2,-1\right>, \left<2,-4,2,1\right>, \left<-3,5,-4,-1\right> \right\rbrace.$$ A basis for the subspace $H \subseteq \mathbb{R}^{4}$ is $\big\lbrace$ $\big\rbrace$. vector