Wieder einmal wurde ich mit der Aufgabe betraut …
und wieder einmal hilft ein Blick in die Hilfe 
Bei der Hilfe zu „lm“ steht unter „Arguments“:
formula: an object of class „formula“ (or one that can be coerced to that class): a symbolic description of the model to be fitted. The details of model specification are given under Details.
Und dann steht da unter „Details“:
Models for lm are specified symbolically. A typical model has the form response ~ terms where response is the (numeric) response vector and terms is a series of terms which specifies a linear predictor for response. A terms specification of the form first + second indicates all the terms in first together with all the terms in second with duplicates removed. A specification of the form first:second indicates the set of terms obtained by taking the interactions of all terms in first with all terms in second. The specification first*second indicates the cross of first and second. This is the same as first + second + first:second.
Was Du vielleicht nicht verstanden hast, ist, dass x[,1:5] kein Term ist. Ein Term wäre x[,1]+x[,2]+x[,3]+…
Das steht aber auch nochmal genauer in der Hilfe zu „formula“ (die ja verlinkt ist).
LG
Jochen
