If \( \frac{(n+4)!-(n+3)!}{(n+2)!}=144 \), what is the value of (n)?

Correct answer: 9

Using \((n+4)!=(n+4)(n+3)!\), the numerator becomes \((n+3)![(n+4)-1]=(n+3)!(n+3)\). Hence the expression is \(\frac{(n+3)!(n+3)}{(n+2)!}=(n+3)^2\). Therefore, \((n+3)^2=144\). Since \(n\) must be a non-negative integer for the factorials here, \(n+3=12\), giving \(n=9\). The root \(n+3=-12\) gives \(n=-15\), which is not valid. Exam tip: In factorial questions, first expand the larger factorial in terms of the smaller one and cancel common factors.