{m : Type u_2} →
  {n : Type u_3} →
    {α : Type u_4} →
      [inst : Fintype m] →
        [inst_1 : Fintype n] →
          [inst_2 : DecidableEq m] →
            [inst_3 : DecidableEq n] →
              [inst_4 : CommRing α] →
                (A : Matrix m m α) →
                  (B : Matrix m n α) →
                    (C : Matrix n m α) →
                      (D : Matrix n n α) →
                        [inst_5 : Invertible A] → [Invertible (Matrix.fromBlocks A B C D)] → Invertible (D - C * ⅟A * B)