Let ‘E’ be the required expression. Then, we have
x2 – xy + y2– x + y + 3 – E = – x2 + 3y2 – 4xy + 1
Therefore, E = (x2 – xy + y2– x + y + 3) – (- x2 + 3y2 – 4xy + 1)
= x2 – xy + y2– x + y + 3 + x2 – 3y2 + 4xy – 1
Collecting positive and negative like terms together, we get
= x2 + x2– xy + 4xy + y2– 3y2 – x + y + 3 – 1
= 2x2+ 3xy- 2y2– x + y + 2