Proof of `Compatibility and codimension of forward/reverse matrix restrictions` (1st statement)
groundedproofs/Lax342547Proofs/MixerCompatibility.lean · lax-342547
What this proof establishes
no assumptions
Assuming the claims on the left, the claim on the right holds — checked by the archive's pipeline. Proof code is not displayed here.
Description
Choose left inverses UZ=1 and VW=1. For compatible A,B the explicit matrix UᵀA + BV - Uᵀ(ZᵀB)V has both prescribed restrictions. Necessity is associativity of matrix multiplication.