Question

Give combinatorial proof to show that

( n k)=(n−1 k−1)+(n−1 k )

Answer 1

Answer:This is certainly a valid proof, but also is entirely useless. Even if you understand the proof perfectly, it does not tell you why the identity is true. A better approach would be to explain what  

(

n

k

)

means and then say why that is also what  

(

n

−

1

k

−

1

)

+

(

n

−

1

k

)

means

Step-by-step explanation: