Question 9The coefficients in $(x+y)^n$ are related to Pascal’s triangle shown below. For example, $(x+y)^3=x^3+3x^2y+3xy^2+y^3$, whose coefficients $1,3,3,1$ form the fourth row. What is the sum of the coefficients of $(x+y)^8$? 128256512127None of the above
