因为,5*6 = (5×c+6)/(5×6) ,6*5 = (6×c+5)/(6×5) ,而且,5*6 = 6*5 ,所以,(5×c+6)/(5×6) = (6×c+5)/(6×5) ,解得：c = 1 ,可得：a*b = (a×c+b)/(a×b) = (a+b)/(a×b) ；因为,3*2 = (3+2)/(3×2) = 5/6 ,4*5 ...