  In the book, I considered differential equations of order $1$ over Banach
$D$\Hyph algebra: differential equation solved with respect to the derivative;
exact differential equation; linear homogeneous equation. I considered examples
of differential equations in quaternion algebra. In order to study homogeneous
system of linear differential equations, I considered vector space over
division $D$-algebra, solving of linear equations over division $D$-algebra and
the theory of eigenvalues in non commutative division $D$-algebra.
