Hint: expand according to the Binomial formula.
Hint: expand according to the Binomial formula.
it does not worth yelling just think a n-length digit that should be composed of 1 or 0's. We can determine how many digit can we write starting from chhosing the place of zero's.. or just determining each place's possible number(as zero or one.)
So first way will give you the function you say and other one will give you 2^n