1. The problem statement, all variables and given/known data 2. Relevant equations Formula => C(n,r) or nCr =n!/r!(n-r)! & the basic Binomial Theorem formula. *Answer mentioned in book = nx 3. The attempt at a solution The LHS should be (x+y)n & the given question is its expansion only if that 'r' is not multiplied in the question. I also know how to add using the summation feature but I am not able to get x+y in the expansion (so I could substitute the value of 1). If I substitute 1 on the LHS I get => 1n.