1) ((m+n-m+n)\(m-n)(m+n))\(2\(3(m-n)))=(2n*3(m-n))\(2(m-n)(m+n))=3n\(m+n)
2) 3a-7b-6a+8b=-3a+b
3(4x+2)-6=12x+6-6=12x
(3x+1)+(x-4)=3x+1+x-4=4x-3
2(2y-1)-3(y+2)=4y-2-3y-6=y-8
(x-2y)(xˇ2+4yˇ2)(x+2y)-xˇ4=(x-2y)x+2y)(xˇ2+4yˇ2)-xˇ4=
=(xˇ2-4yˇ2)(xˇ2+4yˇ2)-xˇ4=
=xˇ4-16yˇ4-xˇ4=-16yˇ4