Question

1.在正数数列{an}中,a1=1,且点（√an,√an-1）(n≥2,n∈N+)在直线x-√2y=0上,则前n项和Sn

Answer 1

1)点（√an,√an-1）(n≥2,n∈N+)在直线x-√2y=0上

√an-√2√an-1=0 an=2a(n-1) 等比数列,q=2,a1=1

Sn=2^n-1

2)郁闷,做了半天,题目错了

a^2+b^2=c^2+bc同除c^2

(b/c)^2-b/c+(a/c)^2-1=0

(b/c)^2-b/c+√3/2=0

判别式=1-2√3