What should be added to `x^(4)-x^(2)+x+2` to get `x^(2)+x+4`?

What should be added to 1+2x-3x^(2) to get x^(2)-x-1 ?

What should be added to x^(2) - y^(2) +2xy to obtain x^(2) + y^(2) + 5xy ?

What should be subtracted from 1+x-x^(2) to get 2x+x^(2) ?

What must be added to 2x^(2)-3xy+5y^(2) to get x^(2)-xy-y^(2) ?

What should be subtracted from 2x^(2)-y^(2)+4z^(2) to get x^(2)+y^(2)-z^(2) ?

What should be added to x^2+xy+y^2 to obtain 2x^2+3xy ?

What should be added to 3x^2+4 to get 9x^2-7? (a) 6x^2-11\ (b) 6x^2+11 (c) 12 x^2-11 (d) 12 x^2+11

What should be added to x y-3y z+4z x to get 4x y-3z x+4y z+7?

What number should be added to x^(3)-9x^(2)-2x+3 so that the remainder may be 5 when divided by (x-2) ?

What should be added to x y+y z+z x to get x y-y z-z x ? (a) -2x y-2y z-2z x (b) -3x y-y z-z x (c) -3x y-3y z-3z x (d) 2x y+2y z+2z x