Respuesta :

crackedmoonlight
Simplify to 12-6i-42i+21i^2 and then to 21i^2+48i+12
sdmatera
Here you just distribute and solve
12-42i-6i+21i^2
12-48i+21i^2 (combine like terms)

And remember that i^2 is the same as -1, so we can rewrite it:
12-48i+21(-1)
12-48i-21
-9-48i (combine like terms)

Hope this helps