Tìm y, biết:
( y+ \(\frac{1}{2x3}\)) + ( y + \(\frac{1}{3x4}\)) +( y+\(\frac{1}{4x5}\)) + ( y +\(\frac{1}{5x6}\) ) + ( y + \(\frac{1}{6x7}\)) + ( y+ \(\frac{1}{7x8}\)) =\(\frac{29}{8}\)
\(\frac{1}{1x2}+\frac{1}{2x3}+\frac{1}{3x4}+\frac{1}{4x5}+\frac{1}{5x6}+\frac{1}{6x7}+\frac{1}{7x8}+\frac{1}{8x9}+\frac{1}{9x10}\)
\(y=\frac{1}{1x2}+\frac{1}{2x3}+\frac{1}{3x4}+\frac{1}{4x5}+\frac{1}{5x6}\)
Hảy cho biết y là bao nhiêu
lời giải đầy đủ
y=\(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\)
y=\(1-\frac{1}{6}\)
y=\(\frac{5}{6}\)
\(\Rightarrow y=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\)
\(\Rightarrow y=1-\frac{1}{6}=\frac{5}{6}\)
Vậy \(y=\frac{5}{6}\)
Nhưng hãy cho mình biết làm thế nào để làm ảnh đại diện
trả lời xong rồi mình sẽ giải giúp bạn
(làm thế nào để đưa câu hỏi của mình lên online math)
..................................................................
\(A=\frac{5}{1x2}+\frac{5}{2x3}+\frac{5}{3x4}+\frac{5}{4x5}+\frac{5}{5x6}+\frac{5}{6x7}+\frac{5}{7x8}\)
Ai nhanh mk tick nha!
\(A=\frac{5}{1.2}+\frac{5}{2.3}+...+\frac{5}{7.8}\)
\(\Rightarrow5A=\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{7.8}\)
\(\Rightarrow5A=1.\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-...-\frac{1}{8}\right)\)
\(\Rightarrow5A=1-\frac{1}{8}\)
\(\Rightarrow A=\left(1-\frac{1}{8}\right).\frac{1}{5}=\frac{7}{40}\)
\(A=\frac{5}{1.2}+\frac{5}{2.3}+...+\frac{5}{7.8}\)
\(A=5\left(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{5}{7.8}\right)\)
\(A=5\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{7}-\frac{1}{8}\right)\)
\(A=5\left(1-\frac{1}{8}\right)\)
\(A=5.\frac{7}{8}\)
\(A=\frac{38}{8}\)
nhầm rồi :)
\(A=5.\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-....-\frac{1}{8}\right)\)
\(\Rightarrow A=\frac{5.7}{8}\)
\(\Rightarrow A=\frac{35}{8}\)
Tính nhanh
A = \(\frac{3}{1x2}+\frac{7}{3x4}+\frac{11}{5x6}+\frac{15}{7x8}\) và B = \(\frac{5}{2x3}+\frac{9}{4x5}+\frac{13}{6x7}\)
a, \(\frac{1}{5x6}+\frac{1}{6x7}+\frac{1}{7x8}+\frac{1}{8x9}+\frac{1}{9x10}\)
b ,\(\frac{2}{10x12}+\frac{2}{12x14}+\frac{2}{14x16}+.........+\frac{2}{998x1000}\)
.c, \(\frac{4}{1x2}+\frac{4}{2x3}+\frac{4}{3x4}+........+\frac{4}{69x90}\)
Các bạn giúp mình nhé !
a) \(\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}\)
\(=\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}\)
\(=\frac{1}{5}-\frac{1}{10}\)
\(=\frac{1}{10}\)
b) \(\frac{2}{10.12}+\frac{2}{12.14}+\frac{2}{14.16}+...+\frac{2}{998.1000}\)
\(=\frac{1}{10}-\frac{1}{12}+\frac{1}{12}-\frac{1}{14}+\frac{1}{14}-\frac{1}{16}+...+\frac{1}{998}-\frac{1}{1000}\)
\(=\frac{1}{10}-\frac{1}{1000}\)
\(=\frac{99}{1000}\)
c) \(\frac{4}{1.2}+\frac{4}{2.3}+\frac{4}{3.4}+...+\frac{4}{69.90}\)
\(=4.\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{89.90}\right)\)
\(=4.\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{89}-\frac{1}{90}\right)\)
\(=4.\left(1-\frac{1}{90}\right)\)
\(=4.\frac{89}{90}\)
\(=\frac{178}{45}\)
_Chúc bạn học tốt_
a) 1/10
b) ............
c)............
Mình giúp rồi t.i.c.k mình :v
Tìm y biết:
a) (y+2):5-5x5=378
b) (7,56x0,99+7,56x0,01)x(y+2)=18,9
c) (y+\(\frac{1}{1x2}\))+(y+\(\frac{1}{2x3}\))+(y+\(\frac{1}{3x4}\))+...+(y+\(\frac{1}{2013x2014}\))=\(\frac{2013}{2014}\)
a)(y+2):5-5x5=378
(y+2):5-25=378
(y+2):5=378+25
(y+2):5=403
(y+2)=403x5
y+2=2015
y=2015-2
y=2013
(y+2):5-5.5=378
(y+2):5-25=378
(y+20)=378+25
(y+2)=403
(y+2)=403.5
y+2=2015
y=2015-2
y=2013
a) \(\left(y+2\right):5-5.5=378\)
\(\left(y+2\right):5-25=378\)
\(\left(y+2\right):5=378+25\)
\(\left(y+2\right):5=403\)
\(y+2=403.5\)
\(y+2=2015\)
\(y=2015-2\)
\(y=2013\)
\(\frac{1}{2x3}\)+\(\frac{1}{3x4}\)+\(\frac{1}{4x5}\)+\(\frac{1}{5x6}\)
=\(\frac{3-2}{2x3}\)+\(\frac{4-3}{3x4}\)+\(\frac{5-4}{4x5}\)+\(\frac{6-5}{5x6}\)
Làm tiếp phần còn lại của phép tính ?
\(\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+\frac{1}{5\times6}\)
\(=\frac{3-2}{2\times3}+\frac{4-3}{3\times4}+\frac{5-4}{4\times5}+\frac{6-5}{5\times6}\)
\(=\frac{3}{2\times3}-\frac{2}{2\times3}+\frac{4}{3\times4}-\frac{3}{3\times4}+\frac{5}{4\times5}-\frac{4}{4\times5}+\frac{6}{5\times6}-\frac{5}{5\times6}\)
\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\)
\(=\frac{1}{2}-\frac{1}{6}\)
\(=\frac{1}{3}\)
\(\frac{1}{3x4}\)+ \(\frac{1}{4x5}\) + \(\frac{1}{5x6}\) + \(\frac{1}{6x7}\)+ ............. + \(\frac{1}{11x12}\) = ?
\(\frac{1}{3x4}\) + \(\frac{1}{4x5}\) + \(\frac{1}{5x6}\) + \(\frac{1}{6x7}\)+.........+\(\frac{1}{11x12}\)
ta tính nhanh như sau
1/3+1/12=5/12
vậy tổng trên =5/12 nhớ k hoặc kết bạn vs minh nha
Ta có : \(\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+.....+\frac{1}{11.12}\)
\(=\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+....+\frac{1}{11}-\frac{1}{12}\)
\(=\frac{1}{3}-\frac{1}{12}\)
\(=\frac{4}{12}-\frac{1}{12}=\frac{1}{4}\)