Solution - Simplification or other simple results

Step  1  :

Equation at the end of step  1  :

  ((3•5x2) -  16x) -  15

Step  2  :

Trying to factor by splitting the middle term

 2.1     Factoring  15x²-16x-15 

The first term is,  15x²  its coefficient is  15 .
The middle term is,  -16x  its coefficient is  -16 .
The last term, "the constant", is  -15 

Step-1 : Multiply the coefficient of the first term by the constant   15 • -15 = -225 

Step-2 : Find two factors of  -225  whose sum equals the coefficient of the middle term, which is   -16 .

Step-3 : Rewrite the polynomial splitting the middle term using the two factors found in step 2 above,  -25  and  9 
                     15x² - 25x + 9x - 15

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

Final result :

  (3x - 5) • (5x + 3)