Write a single equation (using only x and y) that is equivalent to each pair of parametric equations.
a. x = 2t - 3
y = t + 2
b. x = t2
y = t + 1
c. x = 1/2t + 1
y = t - 2 / 3
d. x = t - 3
y = 2(t - 1)2