Perform and simplify

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$6x+3y-(5x+2y+3z)+(-4x-3y)=$
$(4x^3-2x^2+x+1)-(-x^2+3x^3-x-7)-(x^3-4x^2+8+2x))=$
$(x+2y-6x)- [3y-(6x-6y) ] - [(x-3y)-(2x+5y) ] = $
$2a-(3b+3c)- {5b-(6c-6b)+5c-[4a-(2c-5b) ]}= $
$(a+b-c)c+(a-b+c)b+(-a+b+c)a-2[a(b-a)+b(c-b)+a(a-c)] =$
$[x^2+(n-1)x+1]x + [x^2-(n-1)x+1]x =$
$x[2x+y-(x+2y)]+x[3x-2y-(2x-3y)]-x[x+3y-(2x+2y)]=$
$-2ab^2c^2(4a^3-3b^2+c) =$
$91a^2b^2c^2-7a^2b(13bc^2-9b^2c)-21b^3c(3a^2-2c^2) =$
$13a^2y^2(8a^5y^7-2a^4y^9)-2a^4y^5(9a^3y^4-13a^2y^6)) =$
$(2a+3c)(5a-3c) =$
$(5a^2b+9ab^2)(3a+4b) =$
$x(2x^2-3y^2)(5x^3-4y^3) =$
$(2a^3+4a^2+8a+16)(3a-6) =$
$(4a^2+2ab+b^2)(2a-b)(8a^3+b^3) =$
$(a+2b)^2 =$
$y(x+y)^3 =$