Extra explanation

Introduction: A function of the form $y(x)=x^k$, with $k$ a non-negative integer is called a positive integer power function.

Extra explanation 1: $x^k$ means that $x$ is multiplied $k$-times by itself. Hence, $x^k=x \cdot x \cdot \ldots \cdot x$ ($k$-times) for a positive integer $k$.

Extra explanation 2: By definition $x^0=1$.

Extra explanation 3: For every positive integer power function is $x=0$ the only zero.