How to solve this?

Question

The area A (in square feet) of the rectangular shed is given by 6x³+7x²+11x+21.And one side of the rectangular is 2x+3. Use polynomial long division to find an expression for the length (in feet) of the shed. 

Answer 1

            3x^2  -x  +7

           ______________________

  2x+3 l 6x^3+7x^2+11x+21

             6x^3+9x^2

             __________

                      -2x^2+11x

                      -2x^2-3x

                      __________

                                 14x+21

                                 14x+21

                                 _______

                                           0