You need to find a such as, for all . Notice that,Originally Posted byLazarath

if and only if, (divide by ) thus, postive the sign does not change

if and only if,

if and only if,

if and only if, for all

(1)

If and (1) is true for then it is true for too. Thus, if (1) is true for the smallest then it is true for all integers bigger than it. Thus, it must be true for 2.

Thus,

Thus, solving for .

Now we check whether is a solution. Thus, . Since it is true for it is true for all as explained in the previous paragraph.