MODERATE EXERCISES

(3) Using the basic rules BR1 - BR12, show that the following property of real numbers holds:

 If a > 0 and b > c, then ab > ac. 

                                a > 0 and b > c

implies                       a > 0 and b - c > 0

which implies                   a( b - c ) >              BR-12

which implies                     ab - ac > 0         

which implies                       ab > ac.