system

 

Real numbers a and b satisfy  

a + ab = 250  

a - ab = -240  

Enter all possible values of a, separated by commas.  

 

You probably won't find a simpler problem than this in your whole math textbook.  

 

                                                       a + ab  =    250  

                                                       a – ab  =  –240  

Just add them together  

                                                      2a         =     10  

Divide both sides by 2  

                                                                a  =  5   

That's it.  

That's all the possible values.  

_.

If you add the two systems, you get 2a=10, so a=5.

I'm pretty sure that is the only value of a (correct me if I am wrong).