Mathematics

Problem

Pascal’s rule relates three consecutive binomial coefficients in two adjacent rows of Pascal’s triangle. Which of the following is Pascal’s rule? a)

{n\choose k} = {n\choose k-1} + {n-1\choose k}

{n\choose k} = {n-1\choose k-1} + {n-1\choose k}

{n\choose k} = {n-1\choose k} + {n-1\choose k+1}

{n\choose k} = {n-1\choose k} - {n-1\choose k-1}