How do i find a polynomial whose value will be 1 if you substitute 3 over 2 for x.

well, if p(x) is linear,

ax+b = 1 when x = 3/2, so
3a/2 + b = 1
3a + 2b = 2
so you can have
p(x) = 4x - 5
p(x) = -6x + 10
and so on.

You can use the same method to find conditions on the coefficients so a quadratic or higher-degree polynomial is used.