                                                
                                                                                   
  ①     x3+8x2+17x+10   
   8x   =x2+7x2 17x=7x+10x 
    =x3+x2+7x2+7x+10x+10
                  =x2+ x+1 +7xx+1 +10x+1 
                  =x+1 x+2 x+5 
       
  ②     4x-y 3    x y         4x2+7xy-2y2 9    
      4x2+7xy-2y2= 4x-y  x+2y       4x-y 3      x+2y 3              
  x+2y=x+3x-3x-y+y+2y= 4x-y -3 x-y 
   x+2y  3          