a). ...=[2x+3(2x+3)][2x-3(2x+3)]=...=(8x+9)(-4x-9)= - (4x+9)(8x+9) ;
b). ...=[3(x-2)+2(3x-7)][3(x-2)-2(3x-7)]=...=(9x-20)(-3x+8) ;
c). ...=[2(5x+3)+5(x-2)][2(5x+3)-5(x-2)]=...=(15x-4)(5x+16) ;
d). ...=(2x²-2x+5 + x²+2x+2)(2x²-2x+5-x²-2x-2) =...=(3x²+7)(x²-4x+3)=x(x-1)(3x²+7) ;
e). ... se procedeaza asemanator !