If in the expansion of (1+x)p(1-x)q, the coefficients of x and x2 are 1 and -2, respectively, then p2+q2 is equal to :
(3) 13
Coefficient of x: p-q=1. Coefficient of x2: p(p-1)2-pq+ q(q-1)2=-2 (p-q)2-(p+q)=-4
1-(p+q)=-4 p+q=5 p=3, q=2
p2+q2=13
Answer: (3)
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