Question

（3X的2次方-5XY）+{-X的2次方-[-3XY+2（X的2次方-XY）+Y的2次方]}

Answer 1

（3X^2-5XY）+{-X^2-[-3XY+2（X^2-XY）+Y^2]}

=3X^2-5XY-X^2+3XY-2X^2+2XY+Y^2

=Y^2