Any number that is divisible by 6 is already divisible by 2, but is not necessarily divisible by 12.
Counterexamples include: 6, 18, 30, 42, 54, and so on. You can find more by multiplying 6 by any odd number. However, multiplying 6 by an even number provides another "2" that would make it divisible by 12.
A. 72 degrees (i hope this helped)
If
has to be a solution of the equation, just plug it in:
![(\pm 15i)^2 + [1] = 0 \iff -225 + [1] = 0 \iff [1] = 225](https://tex.z-dn.net/?f=%20%28%5Cpm%2015i%29%5E2%20%2B%20%5B1%5D%20%3D%200%20%5Ciff%20-225%20%2B%20%5B1%5D%20%3D%200%20%5Ciff%20%5B1%5D%20%3D%20225%20)
So, the solutions of
are