English
The operation of forming a matrix by stacking two row blocks is injective in each argument: if fromRows(A1, A2) = fromRows(B1, B2) then A1 = B1 and A2 = B2.
Русский
Операция формирования матрицы путем проStackирования двух блоков по строкам инъективна по каждому аргументу: если fromRows(A1,A2) = fromRows(B1,B2), то A1 = B1 и A2 = B2.
LaTeX
$$$$\operatorname{fromRows}\text{-}\text{injective}:\quad \forall A_1,A_2,B_1,B_2,\; \operatorname{fromRows}(A_1,A_2)=\operatorname{fromRows}(B_1,B_2) \iff A_1=B_1 \wedge A_2=B_2.$$$$
Lean4
theorem fromRows_inj : Function.Injective2 (@fromRows R m₁ m₂ n) :=
by
intro x1 x2 y1 y2
simp [← Matrix.ext_iff]