let a, b, e, d be complex number ; :: thesis: ((a + b) + e) / d = ((a / d) + (b / d)) + (e / d)
thus ((a + b) + e) / d = ((a + b) / d) + (e / d) by Th63
.= ((a / d) + (b / d)) + (e / d) by Th63 ; :: thesis: verum