Factorise :
(i) a2−23a+42.(ii) a2−23a−108(iii) 1−18x−63x2(iv) 5x2−4xy−12y2(v) x(3x+14)+8(vi) 5−4x(1+3x)(vii) x2y2−3xy−40(viii) (3x−2y)2−5(3x−2y)−24(ix) 12(a+b)2−(a+b)−35