3.若數(shù)列{a
n}滿足
≤λ(λ>1,且λ為實(shí)常數(shù)),n∈N
*,則稱數(shù)列{a
n}為P(λ)數(shù)列.
(1)若數(shù)列{a
n}的前三項(xiàng)依次為a
1=2,a
2=x,a
3=9,且{a
n}為P(3)數(shù)列,求實(shí)數(shù)x的取值范圍;
(2)已知{a
n}是公比為q(q≠1)的等比數(shù)列,且a
1>0,記T
n=|a
2-a
1|+|a
3-a
2|+?+|a
n+1-a
n|.
若存在數(shù)列{a
n}為P(4)數(shù)列,使得
≤0成立,求實(shí)數(shù)t的取值范圍;
(3)記無窮等差數(shù)列{a
n}的首項(xiàng)為a
1,公差為d,證明:“0≤
≤λ-1”是“{a
n}為P(λ)數(shù)列”的充要條件.