∵y=t-1
∴t=y+1
t^2=(y+1)^2
∴x=3t^2
∴x=3(y+1)^2
(y+1)^2=x/3
x=3(y+1)^2表示以(0,-1)为中心,(1/12,-1)为焦点的抛物线.