1,2•[-5]

Possible interpretations:

• If comma is a decimal separator (1,2 = 1.2) and [-5] is a scalar/vector with one entry -5, then the product is 1.2 × (-5) = -6. If you must keep the form as a vector, that’s [-6].

• If you meant a dot product, the expression (1,2) · (-5) is not defined as stated (you need vectors of the same dimension, e.g., (1,2) · (-5, 0) = -5).

Could you confirm which interpretation you intended (decimal 1.2 times -5, or a dot product with vectors of matching dimensions)?