①(a+b)(a^2-ab+b^2)=a^3-a^2b+ab^2+a^2b-ab^2+b^3=a^3+b^3②（3xy)^2/xy+(x-y)^2-(x+y)(x-y)=3xy+x^2-2xy+y^2-x^2+y^2=xy+2y^2③(a-b)^2+b(a-b)=(a-b)(a-b+b)=a(a-b)=a^2-ab④(3x+2)(3x-2)-5x(x-1)-(2x-1)^2=9x^2-4-5x^2+5x-4x^2+4x-1=9x-5