Change the following parametric equations into ordinary equations and explain what curves they represent {x=1/(1+t^2) {y=t/(1+t^2)

Change the following parametric equations into ordinary equations and explain what curves they represent {x=1/(1+t^2) {y=t/(1+t^2)

X ^ 2 + y ^ 2 -- X = 0 circle

Change the following parametric equations into ordinary equations and explain what curves they represent,
1) X = 3-2t (t is the parameter) (2) x = cos θ (θ is the parameter)
y=-1－4t y=cos2θ+1
(3) X = t + 1 / T (t is parameter) (4) x = 5cos φ (parameter)
Y = T-1 / T, y = 3sin φ, I hope not to omit too many steps, but my foundation is not very good,

1) X = 3-2t (t is a parameter)
y=-1－4t ②
① X 2 - 2
x-2y=2(3-2t)-(-1-4t)
x-2y=7
∴x-2y-7=0
It's a straight line
(2) X = cos θ (θ is the parameter) ①
y=cos2θ+1 ②
From (2)
y=2cos²θ-1+1
y=2cos²θ
From 1
cosθ=x
∴y=2x² -1