Use acetic acid and sodium acetate to prepare 0.01 M buffer solution with pH 4.50. pK_a=4.75.

We can easily calculate ratio of concentrations of acid and conjugate base, by plugging known values of pH and pK_a into the Henderson-Hasselbalch equation and rearranging:

[A^-]/[HA] = 10^pH-pK_a = 10^4.50-4.75 = 0.562

0.01 M buffer means sum of concentrations of acetic acid and acetate is 0.01 M:

[HA] + [A^-] = 0.01 M

We have two equations in two unknowns, solving them requires just a basic algebra skills and yields

[HA]=0.0064 M

[A^-]=0.0036 M