先求出P1:
因为P1是l与y轴的交点,设 P1= (0,y)
y= 2*0 +1 = 1
所以 P1=(0,1)
(a1,a2) = (0,1)
a1=0,a2=1
2
P1 = (a1,a2)
P2 = (a2,a3)
Pn = (an,an+1)
得,an+1 = 2 an +1
验证 a1= 2^0 -1 =0
a2 = 2^1-1 = 1
说明
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