1/4 (n-6)=1/4n-3/2
$$\dfrac 1 4 (n-6) = \dfrac 1 4n - \dfrac 3 2$$
$$\dfrac n 4 - \dfrac 6 4 = \dfrac n 4 - \dfrac 3 2$$
$$\dfrac n 4 - \dfrac 3 2 = \dfrac n 4 - \dfrac 3 2$$
and as you can see this statement is a tautolgy. It holds true for all n.
+6251 
