To qualify as a polynomial, the expression in question:
* Consists of one or more terms * Variables are only with positive whole exponents* No variables in the denominator of any term (the coefficients however, can be fractions.)In that case the answer is most likely:
16=5x_9
16=_9+5
16 +_5x=_9+5x+_5x
16 + -5x=_9+0