Matrix addition Definition 7.1.1 (Matrix addition) a11...a1n b11..b1n a11+b11.a1n+b1n 十 三 am1...amn bm1...bmn aml十bml..amm+bmm OA+B=B+A. ⊙(A+B)+C=A+(B+C) A+B-C=A-C+B OA+B=C+D→A+B-C=D Tongji University】 3/14Matrix addition . Definition 7.1.1 (Matrix addition) . .   a11 . . . a1n . . . . . . am1 . . . amn   +   b11 . . . b1n . . . . . . bm1 . . . bmn   :=   a11 + b11 . . . a1n + b1n . . . . . . am1 + bm1 . . . amn + bmn   .1 A + B = B + A. .2 (A + B) + C = A + (B + C) 3. A + B − C = A − C + B .4 A + B = C + D ⇒ A + B − C = D (Tongji University) Linear Algebra 3 / 14