Question 90081


    find the value for k so that 9m^2-kn^2 will have the factors 3m+7n and 3m-7n

       If (3m+7n) and (3m-7n) are the factors  then (3m+7n)*(3m-7n)
                                                   = (3m)^2 - (7n)^
                                                   = 9m^2  -  49n^2
                              Therefore 9m^2- kn^2 = 9m^2- 49n^2

                                         hence  k = 49