\(\frac{3}{5.7}+\frac{3}{7.9}+...+\frac{3}{59.61}\)
GIẢI GIÚP MÌNH NHA
b) A = \(\frac{3}{5.7}\)+ \(\frac{3}{7.9}+...+\frac{3}{59.61}\)
Các bạn giải nhanh giúp mình nha. Mình đang cần gấp.!
\(A=\frac{3}{2}\left(\frac{2}{5.7}+\frac{2}{7.9}+...+\frac{2}{59.61}\right)\)
\(=\frac{3}{2}\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{59}-\frac{1}{61}\right)\)
\(=\frac{3}{2}\left(\frac{1}{5}-\frac{1}{61}\right)=\frac{84}{305}\)
\(A=\frac{3}{5.7}+\frac{3}{7.9}+...+\frac{3}{59.61}\) tìm A
\(\Rightarrow A=\frac{3}{2}.\left(\frac{2}{5.7}+\frac{2}{7.9}+....+\frac{2}{59.61}\right)\)
\(\Rightarrow A=\frac{3}{2}.\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+......+\frac{1}{59}-\frac{1}{61}\right)\)
\(\Rightarrow A=\frac{3}{2}.\left(\frac{1}{5}-\frac{1}{61}\right)\)
\(\Rightarrow A=\frac{3}{2}.\frac{56}{305}\)
\(\Rightarrow A=\frac{84}{305}\)
\(A=\frac{3}{5.7}+\frac{3}{7.9}+...+\frac{3}{59.61}?\)
=> A= \(\frac{3}{2}\) .( \(\frac{1}{5}\) - \(\frac{1}{7}\) + \(\frac{1}{7}\) - \(\frac{1}{9}\) +...+ \(\frac{1}{59}\) - \(\frac{1}{61}\))
=> A=\(\frac{3}{2}\) . (\(\frac{1}{5}\) - \(\frac{1}{61}\) ) => A= \(\frac{3}{2}\). \(\frac{56}{305}\) = \(\frac{84}{305}\) Vậy A= \(\frac{84}{305}\)
\(A=\frac{3}{5.7}+\frac{3}{7.9}+...+\frac{3}{59.61}\)
\(=\frac{3}{2}.\left(\frac{2}{5.7}+\frac{2}{7.9}+...+\frac{2}{59.61}\right)\)
\(=\frac{3}{2}.\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{53}-\frac{1}{61}\right)\)
\(=\frac{3}{2}.\left(\frac{1}{5}-\frac{1}{61}\right)\)
\(=\frac{3}{2}.\frac{56}{305}\)
\(=\frac{84}{305}\)
Tính hợp lý : \(M=\frac{3}{5.7}+\frac{3}{7.9}+...+\frac{3}{59.61}\)
M=3.(\(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-....+\frac{1}{59}-\frac{1}{60}\)\(\frac{1}{61}\))
M= 3.(\(\frac{1}{5}-\frac{1}{61}\))
M=\(\frac{168}{305}\)
\(M=\frac{3}{5.7}+\frac{3}{7.9}+...+\frac{3}{59.61}\)
\(M=\frac{3}{2}.\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{59}-\frac{1}{61}\right)\)
\(M=\frac{3}{2}.\left(\frac{1}{5}-\frac{1}{61}\right)\)
\(M=\frac{84}{305}\)
A=\(\frac{3}{5.7}+\frac{3}{7.9}+.....+\frac{3}{59.61}\)=?
\(\frac{2}{3}A=\frac{2}{3}.\left(\frac{3}{5.7}+\frac{3}{7.9}+...+\frac{3}{59.61}\right)\)
\(\frac{2}{3}A=\frac{2.3}{3.5.7}+\frac{2.3}{3.7.9}+...+\frac{2.3}{3.59.61}\)
\(\frac{2}{3}A=\frac{2}{5.7}+\frac{2}{7.9}+...+\frac{2}{59.61}\)
\(\frac{2}{3}A=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{59}-\frac{1}{61}\)
\(\frac{2}{3}A=\frac{1}{5}-\frac{1}{61}\)
\(\frac{2}{3}A=\frac{56}{305}\)
\(A=\frac{56}{305}.\frac{3}{2}\)
\(A=\frac{84}{305}\)
\(A=\frac{3}{5.7}+\frac{3}{7.9}+...+\frac{3}{59.61}\)
\(A=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{3}{59.61}\)
\(A=\frac{1}{5}-\frac{1}{61}\)
\(A=\frac{56}{305}\)
tính
\(N=\frac{3}{5.7}+\frac{3}{7.9}+\frac{3}{9.11}+...+\frac{3}{197.199}\)
giải giúp mih nha
BÀi này dễ thôi bạn ạ
N=3(1/5.7+1/7.9+.........+1/197.199)
N=3/2( 1/5-1/7+1/7-1/9+1/9-..........+1/197-1/199)
N=3/2(1/5-1/199)
N=3/2.194/995
N=291/995
k đúng cho mình nhé
N=3.1/2.(1/5-1/7+1/7-1/9+1/9-1/11+...+1/197-1/199)
N=3.1/2.(1/5-1/99)
N=3.1/2.94/495
N=3.47/495
N=47/165
N=3/5.7+3/7.9+........+3/197.199
=>N=3/2(2/5.7+2/7.9+.....+2/197.199)
=>N=3/2(1/5-1/7+1/7-1/9+........+1/197-1/199)
=>N=3/2(1/5-1/199)
=>N=3/2x194/995=291/995
Thuc hien phep tinh : A= \(\frac{-1}{54}-\frac{3}{1.3}-\frac{3}{3.5}-\frac{3}{5.7}-\frac{3}{7.9}-...-\frac{3}{79.81}\)
GIÚP MÌNH VỚI NHÉ! CẢM ƠN TRƯỚC NHA!!!
tính tổng S=\(\frac{2}{5.7}+\frac{2}{7.9}+...+\frac{2}{59.61}\)
\(=\frac{1}{5}-\frac{1}{61}=\frac{56}{305}\)
\(S=\frac{2}{5.7}+\frac{2}{7.9}+...+\frac{2}{59.61}\)
\(S=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{59}-\frac{1}{61}\)
\(S=\frac{1}{5}-\frac{1}{61}\)
\(S=\frac{61}{305}-\frac{5}{305}\)
\(S=\frac{56}{305}\)
\(S=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{59}-\frac{1}{61}\)
\(S=\frac{1}{5}-\frac{1}{61}\)
\(S=\frac{56}{305}\)
Tính\(\frac{4}{5.7}+\frac{4}{7.9}+...+\frac{4}{59.61}\)
Đặt A=như đã cho.
=>1/2A=2/5*7+2/7*9+2/9*11+...+2/59*61.
=>1/2A=1/5-1/7+1/7-1/9+1/9-1/11+...+1/59-1/61.
=>1/2A=1/5-1/61=56/305.
=>A=56/305*2=112/305.
k nha đúng đó.Có j kb nha.