Assuming [tex]z_1=5[/tex] and [tex]z_2=-6i[/tex], as well as [tex]z_3=3i z_1[/tex] and [tex]z_4 = z_2-2[/tex], we have
[tex]z_3 - z_4 = 3iz_1 - (z_2-2) = 3i\times5 - (-6i-2) = 15i + 6i + 2 = 2 + 21i[/tex]
Since both the real and imaginary parts are positive, [tex]z_3-z_4[/tex] belongs to the first quadrant.
