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in Mathematics by (71.2k points)

In the expansion of (x-y)10, (co efficient of x7y3) - (co-efficient of x3 y7) =_____

(a) 10 C7 

(b) 2 .10 C7 

(c) 10 C7 + 10 C1 

(d) 0

1 Answer

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Best answer

Correct option: (d) 0

Explanation:

given (x – y)10 

coefficient of x7y3 – coefficient of x3y7 

= coefficient of T4 – coefficient of T8 ------ (r = 3, r = 7 respectively)

= 10C3 x10–3 ∙ y310C7 x10–7 ∙ y7 

= 10C7 x7y310C7 x3y7 

i.e. 10C710C7 = 0

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