It is given that z = 3i(7-i)(i+1). Show that z can be written in the form 24i - k. State the integer k.

z = 3i(7-i)(i+1)= 3i(7i-i+7-i² )= 3i(6i+8)= 18i² +24 (1 method mark)= 24i-18 (1 method mark)k=18 (1 answer mark)