1. Because it is the second term, that is, the coefficient of the second term is set to R, the first term is Cn0, and the second term is Cn 1 (this is how books are set).

Cnr = 8 = & gtCn 1=8 = >n=8

2.cnr[x^(- 1)]^r*x^(n-r)=cnr*x^(n-2r)

Constant term, so n-2r=0 r=4.

So the constant term is C84=8! /(4! *4! )=(8*7*6*5)/(4*3*2* 1)=70

If you think it's good, please adopt it. Thank you.