i) (A – B) – C
(A – B) = (4x2 + y2 – 6xy) – (3y2 + 12x2 + 8xy)
= (4x2 – 12x2) + (y2 – 3y2) + ( – 6xy – 8xy)
A – B = – 8x2 – 2y2 – 14xy
∴ (A – B) – C = ( – 8x2 – 2y2 – 14xy) – (6x2 + 8y2 + 6xy)
= ( – 8x2 – 6x2) + -2y2 – 8y2) + ( – 14xy – 6xy)
= – 14x2 – 10y2 – 20xy
∴ (A – B) – C = – (14x2 + 10y2 + 20xy)
ii) 2A + B
2A = 2(4x2 + y2 – 6xy) = 8x2 + 2y2 – 12xy
∴ 2A + B = (8x2 + 2y2 – 12xy) + (3y2 + 12x2 + 8xy)
= (8x2 + 12x2) + (2y2 + 3y2) + ( – 12xy + 8xy)
∴ 2A + B = 20x2 + 5y2 – 4xy
iii) A – 3B
38 = 3(3y2 + 12x2 + 8xy) = 9y2 + 36x2 + 24xy
∴ A – 3B = (4x2 + y2 – 6xy) – (9y2 + 36x2 + 24xy)
= (4x2 – 36x2) (y2 – 9y2) ( 6xy – 24 xy)
= 32x2 – 8y2 – 30xy
∴ A – 3B = – 32x2 – 8y2 – 30xy (or)
= – [32x2 + 8y + 30xy]