M = - \(\frac{4}{1.5}\) - \(\frac{4}{5.9}\) - ... - \(\frac{4}{n\left(n+4\right)}\)
= - (\(\frac{4}{1.5}\) + \(\frac{4}{5.9}\) + ... + \(\frac{4}{n\left(n+4\right)}\)
= - ( 1 - \(\frac{1}{5}\) + \(\frac{1}{5}\) - \(\frac{1}{9}\) + ... + \(\)\(\frac{1}{n}\) - \(\frac{1}{n+4}\)
= - ( 1 - \(\frac{1}{n+4}\))
= - \(\frac{n+3}{n+4}\)
Tính tổng:\(M:-\frac{4}{1.5}-\frac{4}{5.9}-\frac{4}{9.13}-...-\frac{4}{\left(n+4\right)n}.\)
Tính tổng sau:
M=\(\frac{4}{1.5}-\frac{4}{5.9}-\frac{4}{9.13}-.....-\frac{4}{\left(n-4\right).n}\)
Ai nhanh mk tick
Tính M=\(-\frac{4}{1.5}-\frac{4}{5.9}-\frac{4}{9.13}-...-\frac{4}{\left(n-4\right).n}\)
tính :S=\(\frac{-4}{1.5}-\frac{4}{5.9}-\frac{4}{9.13}......-\frac{4}{\left(n-4\right)n}\left(n\in N\right)\)
Tính S=\(\frac{-4}{1.5}-\frac{4}{5.9}-\frac{4}{9.13}......-\frac{4}{\left(n-4\right)n}\left(n\in N\right)\)
Bài 2 : Tính giá trị biểu thức :
E = - \(\frac{4}{1.5}-\frac{4}{5.9}-\frac{4}{9.11}-..........-\frac{4}{\left(n-4\right)n}\)
TÍNH
M =-\(\frac{4}{1.5}\) - \(\frac{4}{5.9}\)- \(\frac{4}{9.13}\)-.......- \(\frac{4}{\left(n+4\right)n}\)
S=\(\frac{4}{1.5}-\frac{4}{5.9}-\frac{4}{9.13}-..............-\frac{4}{\left(n-4\right)^n}\) (n thuộc N)
GIÚP MK VS MK ĐANG CẦN GẤP
1.Tính:
a,\(A=\frac{1}{1.2}-\frac{1}{2.3}-\frac{1}{3.4}-......-\frac{1}{\left(n-1\right).n}\)\(n\in N\)
b,\(\frac{4}{1.5}-\frac{4}{5.9}-\frac{4}{9.13}-....-\frac{4}{\left(n-4\right).n}\)\(n\in N\)
c\(C=1-\frac{1}{2}-\frac{1}{2^2}-\frac{1}{2^3}-.....-\frac{1}{2^{10}}\)