Which is true about the completely simplified difference of the polynomials a3b + 9a2b2 − 4ab5 and a3b − 3a2b2 + ab5? the difference is a binomial with a degree of 5.
the difference is a binomial with a degree of 6.
the difference is a trinomial with a degree of 5.
the difference is a trinomial with a degree of 6.

Let be A =a3b +9a2b2-4ab5, and B=a3b-3a2b2+ab5,so the difference can be defined as A - B =a3b +9a2b2-4ab5 -(a3b-3a2b2+ab5), when there is negative sign in front of the parathesis, all the inside signs must change: that is as follow: A- B= a3b +9a2b2-4ab5 - a3b + 3a2b2 - ab5= a3b-a3b +9a2b2+3a2b2-4ab5- ab5= 12a2b2 -5ab5, the fist term has 2+2=4, as a degree,the second term has 1 +5 =6, so the true answer : The difference is a binomial with a degree of 6