Which facts could be applied to simplify this expression? Check all that apply. 5 x + 3 y + (negative x) + 6 z To add like terms, add the coefficients, not the variables. First add 5x + x. The simplified expression is 4 x + 3 y + 6 z. Only combine terms which contain the same variable. The simplified expression is 5 x + 3 y + 6 z.