Multiply two like bases possessing exponents by keeping the base the same and adding the exponents. For example, if you have y^9 x y^5, you would add 9 and 5 to get y^14.
Multiply two different exponents applied to a single base by calculating the exponents inside and outside a set of parentheses. For instance, in the case of (y^4)^5, you would multiply 4 by 5 to get y^20.
Distribute an exponent to each base within a set of parentheses by raising that base to the indicated power and then multiplying the bases together. The reverse is true as well. If you have two bases raised to the same power, you can multiply the bases first and then raise them to the power. For example, (2 * 4)^2 equals 2^2 * 4^2. If you square two, you get 4, and if you square 4, you get 16. Therefore, 4 times 16 is 64. This is the same as multiplying 2 by 4 first to get 8 and raising 8 to the second power to get 64.