等差数列7,15,23,31,39等511是第几项

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等差数列7,15,23,31,39等511是第几项

等差数列7,15,23,31,39等511是第几项
等差数列7,15,23,31,39等511是第几项

等差数列7,15,23,31,39等511是第几项
等差数列7,15,23,31,39-----------等
511是第(511-7)/8+1=64项

d=8
(511-7)/8=63
511是第 64 项

a1=7
a2=a1+8
a3=a2+2*8
an=a1+(n-1)*8=511
7+8n-8=511
8n=512
n=64

等差数列7,15,23,31,39 d=8
(511-7)/8=63
所以是第64项,第一项是7