In the expansion of (1+px)n,n∈N, the coefficient of x and x2 are 8 and 24 respectively, then

We have (1+px)n=1+nC1(px)+nC2(px)2+…=1+npx+12n(n−1)p2x2+…According to the hypothesis,               np=8 and 12n(n−1)p2=24Putting p=8/n in the second expression, we get12n(n−1)8n2=24⇒n−1n=24×28×8=34⇒4n−4=3n⇒n=4Putting this value in np=8, we get p=2.