Answer
a) Power of a Product Rule
b) Product Rule
c) Negative Power Rule
Work Step by Step
a) The student used the Power of a Product Rule of the Laws of Exponents, which states that $\left( x^my^n \right)^p=x^{mp}y^{np}.$
b) The student used the Product Rule of the Laws of Exponents, which states that $x^m\cdot x^n=x^{m+n}.$
c) The student used the Negative Power Rule of the Laws of Exponents, which states that $x^{-m}=\dfrac{1}{x^m}$ or $\dfrac{1}{x^{-m}}=x^m.$
