a) A(x)+B(x)−C(x)=x2−0.45x+1.2+0.8x2−1.2x−(1.6x2−2x)=0.22+0.35x+1.2.
b) M(y)−N(y)−P(y)=y2−1.75y−3.2−(0.3y2+4)−(2y−7.2)=0.7y2−0.35y.