[tex]\mathbf r(t)=t\mathbf i+(6t-t^2)\,\mathbf k=x(t)\mathbf i+y(t)\mathbf j+z(t)\mathbf k[/tex]
[tex]\implies z=x^2y^2\iff 6t-t^2=t\times0=0\impiles t(6-t)=0\implies t=0,6[/tex]
At [tex]t=0[/tex], you have [tex]\mathbf r(0)=0\mathbf i+0\mathbf j+0\mathbf k[/tex].
At [tex]t=6[/tex], you have [tex]\mathbf r(6)=6\mathbf i+0\mathbf j+0\mathbf k[/tex].
