What is the product of positive integer and negative integer?

A negative.

Here is a little table, on multiplicatio/ division of positive and negative integers.

• • = +
• • = -

• • = -
• • = +

NB If no sign is given , then read it as positive (+).

e.g.

2 x 2 = (+)4 (No signs so read as (+)).

2 X - 2 = -4

-2 X (+)2 = -4

-2 X -2 = (+)4 .