\(\frac{4}{2\times4}+\frac{4}{4\times6}+\frac{4}{6\times8}+\frac{4}{8\times10}+...+\frac{4}{16\times18}+\frac{4}{18\times20}\)
Những câu hỏi liên quan
Tính nhanh:\(\frac{1\times2\times3+2\times4\times6+3\times6\times9+4\times8\times12+5\times10\times15}{1\times3\times5+2\times6\times10+3\times9\times15+4\times12\times20+5\times15\times25}-\frac{1+2+3+2+4+6+3+6+9+4+8+12+5+10+15}{1+3+5+2+6+10+3+9+15+4+12+20+5+15+25}\)
Bài 4: Tính nhanh:a, A left(frac{84}{13}right)^2+left(frac{35}{13}right)^2 b, B frac{12-frac{12}{7}-frac{12}{289}-frac{12}{85}}{4-frac{4}{7}-frac{4}{289}-frac{4}{85}}divfrac{3+frac{3}{13}+frac{3}{169}+frac{3}{91}}{7+frac{7}{13}+frac{7}{169}+frac{7}{91}}c, C frac{1times2+2times4+3times6+4times8+5times10}{3times4+6times8+9times12+12times16+15times20}
Đọc tiếp
Bài 4: Tính nhanh:
a, A =\(\left(\frac{84}{13}\right)^2+\left(\frac{35}{13}\right)^2\)
b, B = \(\frac{12-\frac{12}{7}-\frac{12}{289}-\frac{12}{85}}{4-\frac{4}{7}-\frac{4}{289}-\frac{4}{85}}\div\frac{3+\frac{3}{13}+\frac{3}{169}+\frac{3}{91}}{7+\frac{7}{13}+\frac{7}{169}+\frac{7}{91}}\)
c, C =\(\frac{1\times2+2\times4+3\times6+4\times8+5\times10}{3\times4+6\times8+9\times12+12\times16+15\times20}\)
tính :\(\frac{1}{1\times2\times3}+\frac{1}{2\times3\times4}+\frac{1}{3\times4\times5}+\frac{1}{4\times5\times6}+\frac{1}{5\times6\times7}+\frac{1}{6\times7\times8}+\frac{1}{7\times8\times9}+\frac{1}{8\times9\times10}\)
\(\frac{1}{1.2.3}+\frac{1}{2.3.4}+...+\frac{1}{8.9.10}=\frac{1}{2}.\left(\frac{1}{1.2}-\frac{1}{2.3}\right)+\frac{1}{2}.\left(\frac{1}{2.3}-\frac{1}{3.4}\right)+...+\frac{1}{2}.\left(\frac{1}{8.9}-\frac{1}{9.10}\right)\)
\(=\frac{1}{2}.\left(\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}+...+\frac{1}{8.9}-\frac{1}{9.10}\right)\)
\(\frac{1}{2}.\left(\frac{1}{1.2}-\frac{1}{9.10}\right)=\frac{1}{2}.\frac{22}{45}=\frac{11}{45}\)
Đúng 0
Bình luận (0)
\(\frac{1}{3\times4}-\frac{1}{4\times5}-\frac{1}{5\times6}-\frac{1}{6\times7}-\frac{1}{7\times8}-\frac{1}{8\times9}-\frac{1}{9\times10}\)
:V Làm sai hết rồi sai ngay từ bước đầu tiên.
\(\frac{1}{3.4}-\frac{1}{4.5}-\frac{1}{5.6}-....-\frac{1}{9.10}\)
\(=\frac{1}{3.4}-\left(\frac{1}{4.5}+\frac{1}{5.6}+....+\frac{1}{9.10}\right)\)
\(=\frac{1}{12}-\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+....+\frac{1}{9}-\frac{1}{10}\right)\)
\(=\frac{1}{12}-\left(\frac{1}{4}-\frac{1}{10}\right)\)
\(=\frac{1}{12}-\frac{3}{20}\)
\(=\frac{-11}{12}\)
Đúng 0
Bình luận (0)
\(\frac{1}{3.4}-\frac{1}{4.5}-...-\frac{1}{9.10}\)
= \(-\left(\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}\right)\)
= \(-\left(\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{9}-\frac{1}{10}\right)\)
= \(-\left(\frac{1}{3}-\frac{1}{10}\right)\)
= \(-\frac{7}{30}\)
Đúng 0
Bình luận (0)
\(=-(\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{9}-\frac{1}{10})\)
\(=-\left(\frac{1}{3}-\frac{1}{10}\right)\)
\(=-\frac{7}{30}\)
~ Hok tốt ~
Đúng 0
Bình luận (0)
Xem thêm câu trả lời
\(\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+\frac{1}{5\times6}+\frac{1}{6\times7}+\frac{1}{7\times8}+\frac{1}{8\times9}+\frac{1}{9\times10}\)
1/2.3+1/3.4+1/4.5+1/5.6+1/6.7+1/7.8+1/8.9+1/9.10
=1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6+1/7-1/7+1/8-1/8+1/9+1/9-1/10
=1/2-1/10
=5/10-1/10
=4/10=2/5
Đúng 0
Bình luận (0)
\(\frac{1}{2x3}+\frac{1}{3x4}+\frac{1}{4x5}+\frac{1}{5x6}+\frac{1}{6x7}+\frac{1}{8x9}+\frac{1}{9x10}\)
\(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}\)
\(\frac{1}{2}-\frac{1}{10}\)
\(\frac{2}{5}\)
Đúng 0
Bình luận (0)
= 1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10
= 1/2-0-0-0-0-0-0-0-0-1/10
=1/2 - 1/10
=2/5
tớ trước nhé
Đúng 0
Bình luận (0)
Xem thêm câu trả lời
So sánh các số :
A=\(\frac{1\times2+2\times4+3\times6+4\times8+5\times10}{3\times4+6\times8+9\times12+12\times16+15\times20}\)
và
B=\(\frac{111111}{666665}\)
giải chi tiết giùm nha
A) \(\frac{1}{6}\) = 0,1666666665
B) 0,1666669167
\(\frac{1}{6}\) < \(\frac{111111}{666665}\)
Bạn lấy tử chia cho mẫu là ra
Đúng 0
Bình luận (0)
\(y=\frac{1\times2\times3+2\times4\times6+4\times8\times12+8\times16\times24}{2\times3\times4+4\times6\times8+8\times12\times16+16\times24\times32}\frac{ }{ }\)
\(y=\frac{1x2x3+2x4x6+4x8x12+8x16x24}{2x3x4+4x6x8+8x12x16+16x24x32}\)
\(y=\frac{1}{4}\)
tích nha . Đúng 100% luôn.
Đúng 0
Bình luận (0)
Xem thêm câu trả lời
tính giá trị biểu thúc : \(\frac{1}{2}\times\frac{2\times6}{3\times6\times8}\times\frac{4\times6}{6\times2\times2}\times\frac{4\times5\times2}{2\times8\times10}\)
\(\frac{1.2.6.4.6.4.5.2}{2.3.6.8.6.2.2.2.8.10}=\frac{1}{96}\)
Đúng 0
Bình luận (0)
Gía trị của biểu thức là : \(\frac{1x2x3x2x2x2x2x3x2x2x2x5x2}{2x3x3x2x4x2x3x2x2x2x2x4x2x5x2}\)= \(\frac{1}{48}\)
Đúng 0
Bình luận (0)
Xem thêm câu trả lời
Tìm x biết \(\frac{4}{2\times4}+\frac{4}{4\times6}+\frac{4}{6\times8}+...+\frac{4}{2008\times2010}+x=\frac{-1}{1005}\)
\(\frac{4}{2\cdot4}+\frac{4}{4\cdot6}+...+\frac{4}{2008\cdot2010}+x=-\frac{1}{1005}\)
\(2\cdot\left(\frac{2}{2\cdot4}+\frac{2}{4\cdot6}+...+\frac{2}{2008\cdot2010}\right)+x=-\frac{1}{1005}\)
\(2\cdot\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+...+\frac{1}{2008}-\frac{1}{2010}\right)+x=-\frac{1}{1005}\)
\(2\cdot\left[\left(\frac{1}{2}-\frac{1}{2010}\right)+\left(\frac{1}{4}-\frac{1}{4}\right)+\left(\frac{1}{6}-\frac{1}{6}\right)+...+\left(\frac{1}{2008}-\frac{1}{2008}\right)\right]+x=-\frac{1}{1005}\)\(2\cdot\left[\left(\frac{1005}{2010}-\frac{1}{2010}\right)+0+...+0\right]+x=-\frac{1}{1005}\)
\(2\cdot\frac{1004}{2010}+x=-\frac{1}{1005}\)
\(\frac{1004}{1005}+x=-\frac{1}{1005}\)
\(x=-\frac{1}{1005}-\frac{1004}{1005}=-1\)
Vậy x=-1
Chúc bạn học tốt!^_^
Đúng 0
Bình luận (0)