Multilinear Maps of V^n into Reals and Effect of Linear Transforma

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Hi, All:

Is there a "nice" , non-messy way of showing this:

Let [itex]M(v_1,v_2,..,v_n) → R<sup>+</sup>[/itex], where R is the Reals, be a multilinear map,

where [itex]v_i[/itex] are vectors in a finite-dimensional vector space V.

Now, let [itex]L: V<sup>n</sup> → V<sup>n</sup>[/itex] be a linear map with Det(L)>0 .

How do we show that [itex]M(L(v_1,v_2,..,v_n))([/itex] is also strictly-positive? I think it

has to see with the fact that the map L preserves the orientation of [itex]V<sup>n</sup>[/itex],

but I don't see how to make this more rigorous. Any ideas?
 
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I would write ##M,L## as tensors and search whether there are some nice formulas which connect tensors and determinantes, or otherwise go the hard way by coordinates.