Hi, I need a hint to start this problem:
Expand all the brackets and collect like terms, you should get...
Recall that ? Using this we get...
Now, assuming a, b, c, x, y and z are all real... we have 3 square terms adding to become 0. Since a square term is never non-negative... all the terms must be 0.
So we have which gives or .
Similarly, gives ,
and gives .