in order to find out the different types of gametesproduced by a pea plant having the genotype AaBb,it should be crossed to a plant with genotype

1.aaBB

2.AaBb

3.AABB

4.aabb

If cross with all Dominant genes ,
we can easily findout the Next offspring and its characters.
the question must be changed i feel.

To Know the typesof gametes no need to cross half of the genes they have is the type of gametes.
In any genotype.

For an Pea plant with genotype AaBb
AB;
Ab;
aB;
ab are four types of gametes.