Simplify the following:
(i) (1.5x−4y)(1.5x+4y+3)
(ii) (x+y)(2x+y)+(x+2y)(x−y)
(iii) (a2+5)(b3+3)+5
(i) (1.5x−4y)(1.5x+4y+3)
=(1.5x×1.5x)+(1.5x×4y)+(1.5x×3)−(4y×1.5x)−(4y×4y)−(4y×3)
=2.25x2+6xy+4.5x−6xy−16y2−12y
=2.25x2−16y2+4.5x−12y
(ii) (x+y)(2x+y)+(x+2y)(x−y)
=(x×2x)+(x×y)+(y×2x)+(y×y)+(x×x)−(x×y)+(2y×x)−(2y×y)
=2x2+xy+2xy+y2+x2+xy−2y2
=3x2+4xy−y2
(iii) (a2+5)(b3+3)+5
=(a2×b3+a2×3+5×b3+5×3)+5
=a2b3+3a2+5b3+15+5
=a2b3+3a2+5b3+20