Let
P(x)=4.5x3−2.3x2+7x−1,
Q(x)=−3.2x3+5x2−8x+4, and
R(x)=0.7x3−3x2+x−6.
(i) Find the polynomial S(x)=P(x)−(Q(x)−R(x)) and simplify it completely by combining like terms.
(ii) Rewrite S(x) obtained in part (i) in descending powers of x.
(iii) State the coefficient of x2 in the simplified form of S(x). Do not recompute the entire expression; use your result from part (i).