已知等差数列an绝对值,an+1=2an-3n+1.则第五项a5=
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/04 22:37:55
![已知等差数列an绝对值,an+1=2an-3n+1.则第五项a5=](/uploads/image/z/1270286-62-6.jpg?t=%E5%B7%B2%E7%9F%A5%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97an%E7%BB%9D%E5%AF%B9%E5%80%BC%2Can%2B1%3D2an-3n%2B1.%E5%88%99%E7%AC%AC%E4%BA%94%E9%A1%B9a5%3D)
已知等差数列an绝对值,an+1=2an-3n+1.则第五项a5=
已知等差数列an绝对值,an+1=2an-3n+1.则第五项a5=
已知等差数列an绝对值,an+1=2an-3n+1.则第五项a5=
an=3n,a5=15
a(n+1)=2an-3n+1
an=2a(n-1)-3(n-1)+1
相减:
a(n+1)-an=2an-3n+1-2a(n-1)+3(n-1)-1=2an-2a(n-1)+3
a(n+1)-an=2[an-a(n-1)]+3
a(n+1)-an+3=2[an-a(n-1)+3]
an-a(n-1)+3=(a2-a1+3)2^(n-2)
表达清楚1点,看不懂呀?