1)( 4x^2-5x-2)+(-2+3x-x^2)= 4x^2-5x-2-2+3x-x^2=3x^2-2x-4
2)(a^2+2c-b)-(3a^2-b)=a^2+2c-b-3a^2+b=-2a^2+2c
3)(2.5xy^2-5y+1.25xy)*(2x^2y)=5x^3y^3-10x^2y^2+2.5x^3y^2
4)(5y-1)(y^2-y+2)=5y^3-5y^2+10y-y^2+y-2=5y^3-6y^2+11y-2
5)(2c+3)(2c+3)-(c+5)(c+1)=4c^2+12c+9-c^2-6c-5=3c^2+6c+4