[tex]a)\\\\ (m+n)(m-2)+(m-n)(m+1)=m^2-2m+mn-2n+m^2+m-mn-n=\\\\=2m^2-m-3n\\\\b)\\\\(3x-2)(3x-2y+1)-4x(2x-3y+1)=\\\\=9x^2-6xy+3x-6x+4y-2-8x^2+12xy- 4x=x^2+6xy-7x+4y-2[/tex]
[tex]c)\\\\ 3(m+1)(n-2)+2(n+1)(m-2)=3(mn-2m+n-2)+2(mn-2n+m-2)=\\\\=3 mn-6m+3n-6+2 mn-4n+2m-4=5mn-4m-n-10\\\\d)\\\\x(x+1)(x+2)-x(x-1)(x-2)=x(x^2+2x+x+2)-x(x^2-2x-x+2)=\\\\= x^3+2x^2+x^2+2x- x^3+2x^2+x^2-2x=6x^2[/tex]
