Помогитее!!!!
упростите:
(7-2х-х^2)-(х-2)(х+3)
(3m^2+3n^2)-(2m+n)(m+2n)
(n+1)(2n-3)+(n-1)(3n+1)
(x-y)(2x-3y)-(3x-y)(2x+y)

$(7-2x- x^{2} )-(x-2)(x+3) = 7 - 2x - x^{2} - x^{2} - 3x + 2x +6$ =
= $-2 x^{2} -3x + 11$
$(3m^2+3n^2)-(2m+n)(m+2n) = 3m^2 + 3n^2 - 2m^2 - 4mn -nm - // -2n^2 = n^2 + m^2 - 5mn //$
$(n+1)(2n-3)+(n-1)(3n+1) = 2n^2 -3n +2n -3 +3n^2+n-3n$ $-1 = 5n^2 -3n -3$
$(x-y)(2x-3y)-(3x-y)(2x+y) = 2x^2-3xy-2xy+3y^2-6x^2$ $-3xy+2xy+y^2 = 4y^2 - 4x^2 -6xy$ .