find the conjugate on z times w
if z=[3,120]
and w=[-1,-15]
If [a,b] is your way of writing the complex number a + bi, where a and b are real, then
(3 + 120i)(-1-15i) = -3 + 1800 - 1201 -45i
= 1797 - 165i
The conjugate of that is 1797 + 165i
which you would write [1797,165]