x(t) = 5t2 + (5/3)t - 3
y(t) = 3t2 + t + 3
Multiply the first equation by -3/5:
(-3/5)x(t) = -3t2 - t + 9/5
y(t) = 3t2 + t + 3
Add the equations to get: (-3/5)x(t) + y(t) = 24/5
So, (-3/5)x + y = 24/5
y = (3/5)x + (24/5) = f(x)