4/5.7+4/7.9+...+4/59.61
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tính:4/(5.7)+4/(7.9)+...+4/(59.61)
Tính 4/5.7+4/7.9+...+4/59.61
Ta có :
4/5 . 7 + 4/7 . 9 + ...+ 4/59 . 61
= 2 . ( 2/5 . 7 + 2/7 . 9 + ...+ 2/59 . 61 )
= 2 . ( 1/5 - 1/7 + 1/7 - 1/9 + ...+ 1/59 - 1/61 )
= 2 . ( 1/5 - 1/61 )
= 2 . 56/305
= 112/305
Tham khảo nha !!!
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Tính: 4/5.7 + 4/7.9 + ... + 4/59.61
4/5.7+4/7.9+...+4/59.61
=2.(2/5.7+2/7.9+...+2/59.61)
=2.(1/5-1/7+1/7-1/9+...+1/59-1/61)
=2.(1/5-1/61)
=2.56/305
=112/203
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A=( 2/5.7+2/7.9+.........+2/59.61).2
A = (1/5-1/7+1/7-1/9+.......+1/59-1/61).2
A= ( 1/5-1/61)2
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giai bài S= 4/5.7+4/7.9+...+4/59.61
Ta có:
\(S=\frac{4}{5.7}+\frac{4}{7.9}+\frac{4}{9.11}+...+\frac{4}{59.61}\)
\(=2.\left(\frac{2}{5.7}+\frac{2}{7.9}+...+\frac{2}{59.61}\right)\)
\(=2.\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{59}-\frac{1}{61}\right)\)
\(=2.\left(\frac{1}{5}-\frac{1}{61}\right)\)
\(=2.\left(\frac{61}{305}-\frac{5}{305}\right)\)
\(=2.\frac{56}{305}\)
\(=\frac{112}{305}\)
Vậy \(S=\frac{112}{305}\)
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Tính \(A=\dfrac{4}{5.7}+\dfrac{4}{7.9}+............+\dfrac{4}{59.61}\)
Ta có :
\(A=\dfrac{4}{5.7}+\dfrac{4}{7.9}+............+\dfrac{4}{59.61}\)
\(\dfrac{A}{2}=\dfrac{2}{5.7}+\dfrac{2}{7.9}+..............+\dfrac{2}{59.61}\)
\(\dfrac{A}{2}=\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+.......+\dfrac{1}{59}-\dfrac{1}{61}\)
\(\dfrac{A}{2}=\dfrac{1}{5}-\dfrac{1}{61}\)
\(\dfrac{A}{2}=\dfrac{56}{305}\)
\(\Rightarrow A=\dfrac{112}{305}\)
Chúc bn học tốt!!
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\(A=\dfrac{4}{5.7}+\dfrac{4}{7.9}+...+\dfrac{4}{59.61}\)
\(A=2\left(\dfrac{2}{5.7}+\dfrac{2}{7.9}+...+\dfrac{2}{59.61}\right)\)
\(A=2\left(\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+...+\dfrac{1}{59}-\dfrac{1}{61}\right)\)
\(A=2\left(\dfrac{1}{5}-\dfrac{1}{61}\right)\)
\(A=2.\dfrac{56}{305}\)
\(A=\dfrac{112}{305}\)
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\(A=\dfrac{4}{5.7}+\dfrac{4}{7.9}..........+\dfrac{4}{59.61}\)
\(\dfrac{1}{2}A=\dfrac{2}{5.7}+\dfrac{2}{7.9}+.........+\dfrac{2}{59.61}\)
\(\dfrac{1}{2}A=\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+.....+\dfrac{1}{59}-\dfrac{1}{61}\)
\(\dfrac{1}{2}A=\dfrac{1}{5}-\dfrac{1}{61}\)
\(\dfrac{1}{2}A=\dfrac{56}{305}\)
\(A=\dfrac{112}{305}\)
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Xem thêm câu trả lời
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.
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Xem thêm câu trả lời
\(B=\frac{4}{5.7}+\frac{4}{7.9}+......+\frac{4}{59.61}\) = ?
Ta có 1/2B=2/5.7+2/7.9+...+2/59.61
1/2B=1/5-1/7+1/7-1/9+1/9-...+1/59-1/61
1/2B=1/5-1/61
1/2B=56/305
B=56/305:1/2
B=112/305
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Help me do my homework
\(\frac{4}{5.7}+\frac{4}{7.9}+....+\frac{4}{59.61}\)
= 2/2 . ( 4 / 5.7 +4 / 7.9 +...+ 4 / 59.61 )
= 4/2 . ( 2 / 5.7 +2 / 7.9 +...+ 2 / 59.61 )
= 2 . ( 7-5 / 5.7 + 9-7 / 7.9 +...+ 61-59 / 59.61 )
= 2 . ( 1/5 - 1/7 + 1/7 - 1/9 +...+ 1/59 - 1/61 )
= 2 . ( 1/5 - 1/61 )
= 2 . ( 61/305 - 5/305 )
= 2 . 56/305
= 112/305
ảnh anime đẹp thế là anime gì vậy bạn
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Xem thêm câu trả lời
Tính giá trị các biểu thức:
\(\dfrac{4}{5.7}+\dfrac{4}{7.9}+...+\dfrac{4}{59.61}\)
Đặt A=\(\frac{4}{5.7}\)+\(\frac{4}{7.9}\)+...+\(\frac{4}{59.61}\)
A=2( \(\frac{2}{5.7}\)+\(\frac{2}{7.9}\)+...+\(\frac{2}{59.61}\))
A=2( \(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\)\(\frac{1}{59}-\frac{1}{61}\))
=2( \(\frac{1}{5}-\frac{1}{61}\))=2.\(\frac{56}{305}\)=\(\frac{112}{305}\)
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