3. Let $z_{1}=5+6 i, z_{2}=-i-1$ and $z_{3}=4 i$. (a) Write the following in the form $a+i b$ : i. $2 z_{1}-3 z_{2}+z_{3}$ ii. $z_{1} z_{2} z_{3}$

Step 1 ：\(2z_1 - 3z_2 + z_3 = 2(5+6i) - 3(-i-1) + (4i)\)

Step 2 ：\(= 10 + 12i + 3 + 3i + 4i\)

Step 3 ：\(= 10 + 3 + 12i + 3i + 4i\)

Step 4 ：\(= 13 + 19i\)

Step 5 ：\(z_1 z_2 z_3 = (5+6i)(-i-1)(4i)\)

Step 6 ：\(= ((5+6i)(-i-1))(4i)\)

Step 7 ：\(= (-5i-6i^2 - 5i^2 - 6i^3)(4i)\)

Step 8 ：\(= (-5i + 6 - 5 + 6i)(4i)\)

Step 9 ：\(= (1 + i)(4i)\)

Step 10 ：\(= 4i + 4i^2\)

Step 11 ：\(= 4i - 4\)

Step 12 ：\(= \boxed{-4 + 4i}\)