Precalculus (6th Edition) Blitzer

The different sets of parametric equation are: $x=t,\,y={{t}^{2}}-3\,\text{ and }\,x={{t}^{2}},\,y={{t}^{4}}-3$ (other answers are possible.)
Let us assume, $x=\,t$, then $y={{t}^{2}}-3$ After that, $x=\,{{t}^{2}}$, then $y={{t}^{4}}-3$ Thus, $x=\,t$, $y={{t}^{2}}-3$ and $x=\,{{t}^{2}}$, $y={{t}^{4}}-3$ are two different sets of parametric equations.