Answer:
The answer would be 5!
Explanation:
You start with 1+2i and the conjugate of this would be 1-2i!
After that, in order to find the product, you multiply (1+2i)(1-2i)
You can use distribution or you can use the formula (a+b)(a-b)=a^2-b^2
Either way the answer will be 1-4i^2
i^2=-1 so you replace the i^2 in our equation with negative 1 and solve to get 5!
Hope this helped! <3