Given Equation :

To Find : Value of n

Formula :

By given equation,

By using above formula,

Cancelling terms (n - 4)! And (2!),

∴ (n - 2) × (n - 3) = 6

∴ (n - 2) × (n - 3) = (3) × (2)

By comparing both the sides,

Conclusion : Value of n is 5.

Note : Instead of taking product of two brackets in eq(1), it is easy to convert the constant term that is 6 into product of two consecutive numbers and then by observing two sides of equation we can get value of n.