в) 1. (x^3 - 4^3) / (x^2-4^2) =

      =((x-4)(x^2+4x+16))/((x-4)(x+4))=

      =(x^2+4x+16)/(x+4)

   2. (x^2+10x+25-5x)/x^3-5^3=

       =(x^2+5x+25)/((x-5)(x^2+5x+25))=

       =1/(x-5)

г) 1. x^2+3x+y^2+3y

  2. by-ax

  3. (((x-2)(x+2))/(x^5))*((x^2)/(x+2))=

     = (x-2)/x^3

  4. (((2y-5)(2y+5))/a)*((2y-5)/(2y+5))=

     = ((2y-5)^2)/a