Final answer:
The expressions 4^9, 3^10, 5^3, and y^5 are already in their simplest form, utilizing basic exponent rules which include adding, subtracting, or multiplying exponents depending on the operation.
Step-by-step explanation:
The student asked about simplifying expressions using basic exponent rules. No calculations are required for a) 4^9, b) 3^10, c) 5^3, and d) y^5 as they are already in simplest form. The basic rules of exponents include: when multiplying terms with the same base, add their exponents (3^2 * 3^3 = 3^(2+3) = 3^5); when dividing terms with the same base, subtract the exponents (3^5 / 3^2 = 3^(5-2) = 3^3); when raising an exponent to another power, multiply the exponents ((3^2)^3 = 3^(2*3) = 3^6).