# Question #557cf

##### 1 Answer

n = 6 (which can be verified by substituting n=6 into each side of the equation).

by definition of permutation and multiplying both sides by 3:

factoring out 2's from two of the right side terms:

dividing out the (n+2) and (n+1) terms on both sides:

simplifying:

into standard form:

using the standard formula for quadratic solution:

=

=

=

So,