Factorise :
(i) 6x3−8x2(ii) 35a3b2c+42ab2c2(iii) 36x2y2−30x3y3+48x3y2(iv) 8(2a+3b)3−12(2a+3b)2(v) 9a(x−2y)4−12a(x−2y)3