When you encounter a fraction with the same base raised to different exponents, such as \(\frac{a^m}{a^n}\), you can simplify the expression by subtracting the exponents. This rule is known as the quotient of powers property. Basically, when you're dividing like bases, you subtract the exponent of the denominator from the exponent of the numerator. Hence, \(\frac{a^m}{a^n} = a^{m-n}\). It's important to note that this property only applies when the base of the exponents - the 'a' in our case - is the same.
For instance, in the original exercise \(\frac{a^{4}}{a^{6}}\), applying this property gives us \(a^{4-6} = a^{-2}\).
It's a straightforward and incredibly useful property for simplifying algebraic expressions involving exponents, and it's one you'll encounter frequently in algebra.