=((3x2−4x+1)+(5x2+3x−8))−(4x2−7x+3)
=(3x2−4x+1+5x2+3x−8)−4x2+7x−3
=8x2−x−7−4x2+7x−3
=4x2+6x−10
(ii) B + C - A
=(5x2+3x−8)+(4x2−7x+3)−(3x2−4x+1)
=5x2+3x−8+4x2−7x+3−3x2+4x−1
=5x2+4x2−3x2+3x−7x+4x−8+3−1
=6x2+0x−6=3x2−4x+1+5x2+3x−8+4x2−7x+3
=12x2−8x−4