When do you combine exponents

Adding and Subtracting Powers Rules of Algebra (Laws of Exponents, How to Multiply Add Exponents) You Can Learn Math with Alyssa. Multiplying Variables with Exponents. So, how do we multiply this: (y2)(y3). We know that y2 = yy, and y3 = yyy so let us write out all the multiplies. The exponent "product rule" tells us that, when multiplying two powers that have the same base, you can add the exponents. In this example, you can see how.