The equation of the line joining the complex numbers $-5 + 4i$ and $7 + 2i$ can be expressed in the form

for some complex numbers $a$ and $b$. Find the ordered pair $(a, b)$.

Using the complex notion of slope, you get that a = 1 + 5i and b = 1 - 5i, so ab = (1 + 5i)(1 - 5i) = 1 - 25i^2 = 1 + 25 = 26.