1.

The value of ((100),(0))((200),(150))+((100),(1))((200),(151))+......+((100),(50))((200),(200)) equals (where ((n),(r ))="^(n)C_(r))

Answer»

`((300),(50))`
`((100),(50))((200),(150))`
`((100),(50))^(2)`
`((300),(50))^(2)`

Solution :`(a)` Writing `((200),(r ))=((200),(200-r))`, we have
`((100),(0))((200),(50))+((100),(1))((200),(49))+((100),(2))((200),(48))+......+((100),(50))((200),(0))`
`=` Coefficient of `X^(50)` in the expansion of `(1+x)^(100)(x+1)^(200)`
`=` Coefficient of `x^(50)` in the binomial expansion of `(1+x)^(300)`
`=((300),(50))`


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