A = \(\frac{1}{5}-\frac{3}{7}+\frac{5}{9}-\frac{2}{11}+\frac{7}{13}-\frac{9}{16}-\frac{7}{13}+\frac{2}{11}-\frac{5}{9}+\frac{3}{7}-\frac{1}{5}\)
Ghi cách giải hẳn hoi giúp mik với
Giúp mik 2 bài này với
A = \(\frac{1}{5}-\frac{3}{7}+\frac{5}{9}-\frac{2}{11}+\frac{7}{13}-\frac{9}{16}-\frac{7}{13}+\frac{2}{11}-\frac{5}{9}+\frac{3}{7}-\frac{1}{5}\)
B = \(\frac{1}{100}-\frac{1}{100.99}-\frac{1}{99.98}-\frac{1}{98.97}-...-\frac{1}{3.2}-\frac{1}{2.1}\)
Cố gắng giúp mik giải 1 cách chi tiết nhé
câu b nha
B= 1/100 - (1/2.1 + 1/3.2 + ... + 1/98.97 + 1/99.98 + 1/100.99)
B=1/100 - (1 - 1/2 + 1/2 - 1/3 + 1/3 - ... - 1/99 + 1/99 - 1/100)
B=1/100-(1-1/100)
B=1/100-99/100
B= - 98/100
B= - 49/50
đ ú g nha
- Câu a ~> http://olm.vn/hoi-dap/question/183158.html
Tính nhanh:
\(B=\frac{1}{5}-\frac{3}{7}+\frac{5}{9}-\frac{2}{11}+\frac{7}{13}-\frac{9}{16}-\frac{7}{13}+\frac{2}{11}-\frac{5}{9}+\frac{3}{7}-\frac{1}{5}\)
giúp mình giải bài toán này nha..................
\(\frac{1}{3}-\frac{3}{5}+\frac{5}{9}-\frac{7}{9}+\frac{9}{11}-\frac{11}{13}+\frac{13}{15}+\frac{11}{13}-\frac{9}{11}+\frac{7}{9}-\frac{5}{7}+\frac{3}{5}-\frac{1}{3}\)
Chắc bạn gõ nhầm số hạng thứ 3 phải là +5/7.
Tổng này đối xứng qua 13/15. Các đối xứng trái dấu nên Tổng = 13/15
Tính theo công thức nha bạn
Bài 1: tính nhanh
b) B= \(\frac{1}{5}-\frac{3}{7}+\frac{5}{9}-\frac{2}{11}+\frac{7}{13}-\frac{9}{16}-\frac{7}{13}+\frac{2}{12}-\frac{5}{9}+\frac{3}{7}-\frac{1}{5}\)\(-\frac{1}{5}\)
giải nhanh giúp mình với mình tick cho cảm ơn
\(B=\frac{1}{5}-\frac{3}{7}+\frac{5}{9}-\frac{2}{11}+\frac{7}{13}-\frac{9}{16}-\frac{7}{13}+\frac{2}{12}-\frac{5}{9}+\frac{3}{7}-\frac{1}{5}-\frac{1}{5}\)
\(B=\left(\frac{1}{5}-\frac{1}{5}\right)-\left(\frac{3}{7}-\frac{3}{7}\right)+\left(\frac{5}{9}-\frac{5}{9}\right)+\left(\frac{7}{13}-\frac{7}{13}\right)-\frac{2}{11}+\frac{2}{12}-\frac{9}{16}-\frac{1}{5}\)
\(B=0-0+0+0-\frac{2}{11}+\frac{2}{12}-\frac{9}{16}-\frac{1}{5}\)
\(B=\frac{-2}{11}+\frac{2}{12}-\frac{9}{16}-\frac{1}{5}\)
Đến đây chỉ còn cách quy đồng thôi
bài 3 : Tính nhanh:
B= \(\frac{1}{5}-\frac{3}{7}+\frac{5}{9}-\frac{2}{11}+\frac{7}{13}-\frac{9}{16}-\frac{7}{13}+\frac{2}{11}-\frac{5}{9}+\frac{3}{7}-\frac{1}{5}\)
\(=\left(\frac{1}{5}-\frac{1}{5}\right)+\left(\frac{3}{7}-\frac{3}{7}\right)+\left(\frac{5}{9}-\frac{5}{9}\right)+\left(\frac{2}{11}-\frac{2}{11}\right)+\left(\frac{7}{13}-\frac{7}{13}\right)+\frac{9}{16}\)
= 0 + \(\frac{9}{16}\)
= \(\frac{9}{16}\)
tick nha bn
\(B=\frac{1}{5}-\frac{3}{7}+\frac{5}{9}-\frac{2}{11}+\frac{7}{13}-\frac{9}{16}-\frac{7}{13}+\frac{2}{11}-\frac{5}{9}+\frac{3}{7}-\frac{1}{5}\)
\(=\left(\frac{1}{5}-\frac{1}{5}\right)+\left(-\frac{3}{7}+\frac{3}{7}\right)+\left(\frac{5}{9}-\frac{5}{9}\right)+\left(-\frac{2}{11}+\frac{2}{11}\right)+\left(\frac{7}{13}-\frac{7}{13}\right)-\frac{9}{16}\)
\(=0+0+0+0+0-\frac{9}{16}\)
\(=-\frac{9}{16}\)
^...^ ^_^
cái này đăng hôm qua đến giờ 5 lần rồi,4 câu kia tui làm rồi vô chtt kiém coi có hk
Tính nhanh
\(B=\frac{1}{5}-\frac{3}{7}+\frac{5}{9}-\frac{2}{11}+\frac{7}{13}-\frac{9}{16}-\frac{7}{13}+\frac{2}{11}-\frac{5}{9}+\frac{3}{7}-\frac{1}{5}\)
B=(1/5-1/5) + (-3/7+3/7) + (5/9-5/9) + (-2/11+2/11) + (7/13-7/13) - 9/16
= 0 + 0 + 0 + 0 + 0 - 9/16
=-9/16
B = 1 /5*(-3) /7 + 5 /9*(-2) /11 + 7 /13*(-9) /16*(-7) /13 + 2 /11*(-5) /9 + 3 /7*(-1) /5
B=-9/16
http://coccoc.com/search#query=T%C3%ADnh+nhanh+++B%3D+1%2F+5+%E2%88%92+3%2F+7+%2B+5%2F+9+%E2%88%92+2+%2F11+%2B+7%2F+13+%E2%88%92+9%2F+16+%E2%88%92+7+%2F13+%2B+2%2F+11+%E2%88%92+5%2F+9+%2B+3+%2F7+%E2%88%92+1%2F+5+
Ok
Tính nhanh
B=\(\frac{1}{5}-\frac{3}{7}+\frac{5}{9}-\frac{2}{11}+\frac{7}{13}-\frac{9}{16}-\frac{7}{13}+\frac{2}{11}-\frac{5}{9}+\frac{3}{7}-\frac{1}{5}\)
\(B=\left(\frac{1}{5}-\frac{1}{5}\right)+\left(-\frac{3}{7}+\frac{3}{7}\right)+\left(\frac{5}{9}-\frac{5}{9}\right)+\left(-\frac{2}{11}+\frac{2}{11}\right)+\left(\frac{7}{13}-\frac{7}{13}\right)-\frac{9}{16}\)
\(B=0+0+0+0+0+\left(-\frac{9}{16}\right)=-\frac{9}{16}\)
\(B=\frac{1}{5}-\frac{3}{7}+\frac{5}{9}-\frac{2}{11}+\frac{7}{13}-\frac{9}{16}-\frac{7}{13}+\frac{2}{11}-\frac{5}{9}+\frac{7}{3}-\frac{1}{5}\)
\(B=\left(\frac{1}{5}-\frac{1}{5}\right)+\left(\frac{3}{7}-\frac{3}{7}\right)+\left(\frac{5}{9}-\frac{5}{9}\right)+\left(\frac{2}{11}-\frac{2}{11}\right)+\left(\frac{7}{11}-\frac{7}{11}\right)-\frac{9}{16}\)
\(B=0+0+0+0+0-\frac{9}{16}=-\frac{9}{16}\)
\(A=\frac{1}{3}-\frac{3}{4}-\left(-\frac{3}{5}\right)+\frac{1}{72}-\frac{2}{9}-\frac{1}{36}+\frac{1}{15}\)\(\frac{1}{15}\)
\(B=\frac{1}{5}-\frac{3}{7}+\frac{5}{9}-\frac{2}{11}+\frac{7}{13}-\frac{9}{16}-\frac{7}{13}+\frac{2}{11}-\frac{5}{9}+\frac{3}{7}-\frac{1}{5}\)
TÍNH NHANH:
\(A=\frac{1}{3}-\frac{3}{4}-\left(-\frac{3}{5}\right)+\frac{1}{72}-\frac{2}{9}-\frac{1}{36}+\frac{1}{15}\)
\(B=\frac{1}{5}-\frac{3}{7}+\frac{5}{9}-\frac{2}{11}+\frac{7}{13}-\frac{9}{16}-\frac{7}{13}+\frac{2}{11}-\frac{5}{9}+\frac{3}{7}-\frac{1}{5}\)
A= 1/3- 3/4+ 3/5+ 1/72- 2/9- 1/36+ 1/15
A= ( 1/3- 3/5+ 1/15) - (3/4- 1/72+ 2/9+ 1/36)
A= (5/15- 9/15+ 1/15) - (54/72- 1/72+ 16/72+ 2/36)
A= 1- 71/72
A= 1/72
A = \(\frac{1}{3}\)- \(\frac{3}{4}\) - ( - \(\frac{3}{5}\)) + \(\frac{1}{72}\)- \(\frac{2}{9}\)- \(\frac{1}{36}\)+ \(\frac{1}{15}\)
A = ( \(\frac{1}{3}\)+ \(\frac{3}{5}\)+ \(\frac{1}{15}\)) - ( \(\frac{3}{4}\)- \(\frac{1}{72}\)+ \(\frac{2}{9}\)+ \(\frac{1}{36}\))
A = ( \(\frac{5}{15}\)+ \(\frac{9}{15}\)+ \(\frac{1}{15}\)) - ( \(\frac{54}{72}\)- \(\frac{1}{72}\)+ \(\frac{16}{72}\)+ \(\frac{2}{72}\))
A = 1 - \(\frac{71}{72}\)
A = \(\frac{1}{72}\)