Answer:
b= -3 
b=3/2=1.500
Step-by-step explanation:
step 1 . b • (2b + 3) -  9  = 0 
Step-2 : Find two factors of  -18  whose sum equals the coefficient of the middle term, which is   3 .
      -18    +    1    =    -17  
      -9    +    2    =    -7  
      -6    +    3    =    -3  
      -3    +    6    =    3	
Step-3 : Rewrite the polynomial splitting the middle term using the two factors found in step 2 above,  -3  and  6  
                     2b2 - 3b + 6b - 9
Step-4 : Add up the first 2 terms, pulling out like factors :
                    b • (2b-3)
              Add up the last 2 terms, pulling out common factors :
                    3 • (2b-3)
Step-5 : Add up the four terms of step 4 :
                    (b+3)  •  (2b-3)