How do you evaluate a norm like this?

[GridironCPJ]

‖A(x+αz)-b‖_2^2

where A is an mxn matrix, x and z are vectors in R^n, b is a vector in R^m, and α is a scalar.

 

[Office_Shredder]

I don't really understand the question. A(x+αz)-b is a vector in R^m, so you just calculate its norm