$$( x _ { 1 } - x _ { 0 } ) - 2 ( x _ { 0 } ) ( x _ { 1 } ) ^ { 2 } + ( 3 x _ { 3 } ) ^ { 2 }$$
$9x_{3}^{2}+x_{1}-x_{0}-2x_{0}x_{1}^{2}$
