Problem 8

Problem – 8

Find the coefficient of x^8y^5 in (x+y)^{13}.

 

Solution:

Binomial theorem for (x+y)n = nC0xny0 + nC1xn-1y1+ nC2xn-2y2 + nC3xn-3y3 +…………+ nCn-1x1yn-1+ nCnx0yn

Using the Binomial theorem, coefficient of x8y5 = 13C(13-5) = 13C8 = 1287

 

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