If the coefficients of x and x2 in the expansion of (1 + x)p (1 – x)q, p, q  15, are -3 and -5 respectively, then the coefficient of x3 is equal to…………………

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6 months ago

Coefficient of x in (1+x)p(1x)q=pC0qC1+pC1qC0=3pq=3

Coefficient of x2 in (1+x)p(1x)q=pC0qC2pC1qC1pC2qC0=5

q(q1)2pq+p(p1)2=5q(q1)2(q3)q+(q3)(q4)2=5q=11,p=8

Coefficient of x3 in (1+x)8(1x)11=11C3+8C111C28C211C1+8C3=23

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Maths NCERT Exemplar Solutions Class 12th Chapter One 2025

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