Question

Which is a correct two column proof. Given <4 and

Answer 1

The initial statement is:    QS = SU   (1)

                                    QR = TU    (2)

 

We have to probe that:  RS = ST

 

 

Take the expression (1):                     QS       =   SU

We multiply both sides by R                (QS)R   =   (SU)R

 

 

But    (QS)R = S(QR)     Then:            S(QR)   =   (SU)R     (3)

 

From the expression (2):  QR = TU. Then, substituting it in to expression (3):

 

                                                       S(TU)   =   (SU)R     (4)

 

But  S(TU) = (ST)U  and (SU)R = (RS)U

 

Then, the expression (4) can be re-written as:

 

                                                      (ST)U    =    (RS)U

 

Eliminating U from both sides you have:     (ST) = (RS)    The proof is done.