Solution - Simplification or other simple results

Step  1  :

Equation at the end of step  1  :

  ((3•7x2) -  37x) -  28

Step  2  :

Trying to factor by splitting the middle term

 2.1     Factoring  21x²-37x-28 

The first term is,  21x²  its coefficient is  21 .
The middle term is,  -37x  its coefficient is  -37 .
The last term, "the constant", is  -28 

Step-1 : Multiply the coefficient of the first term by the constant   21 • -28 = -588 

Step-2 : Find two factors of  -588  whose sum equals the coefficient of the middle term, which is   -37 .

Step-3 : Rewrite the polynomial splitting the middle term using the two factors found in step 2 above,  -49  and  12 
                     21x² - 49x + 12x - 28

Step-4 : Add up the first 2 terms, pulling out like factors :
                    7x • (3x-7)
              Add up the last 2 terms, pulling out common factors :
                    4 • (3x-7)
Step-5 : Add up the four terms of step 4 :
                    (7x+4)  •  (3x-7)
             Which is the desired factorization

Final result :

  (3x - 7) • (7x + 4)