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b
Q=\(\frac{2}{6}+\frac{2}{12}+\frac{2}{20}+...+\frac{2}{9900}\)
Rồi giải tương tự như câu a là được
M=\(5\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{99}-\frac{1}{100}\right)=5\left(1-\frac{1}{100}\right)=5.\frac{99}{100}=\frac{99}{20}\)
Bài làm
c ) Ta có :
\(\frac{2017}{2018}< 1\)
\(\frac{12}{11}>1\)
\(\Rightarrow\frac{2017}{2018}< \frac{12}{11}\)
trả lời
a, quy đồng rồi so sánh
b,quy đồng rồi so sánh
c,phân số nào có tử nhỏ hơn mẫu khi so sành với phân số có tử lớn hơn mẫu đều bé hơn
d,quy đồng rồi so sánh
chắc vậy chúc bn học tốt
\(B=\frac{2}{8}+\frac{2}{24}+\frac{2}{48}+...+\frac{2}{18\cdot20}\)
\(B=\frac{2}{2\cdot4}+\frac{2}{4\cdot6}+\frac{2}{6\cdot8}+...+\frac{2}{18\cdot20}\)
\(B=\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+...+\frac{1}{18}-\frac{1}{20}\)
\(B=\frac{1}{2}-\frac{1}{20}\)
\(B=\frac{9}{20}\)
=))
\(A=\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}\)
\(A=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}\)
\(A=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}\)
\(A=\frac{1}{2}+\left(\frac{1}{3}-\frac{1}{3}\right)+\left(\frac{1}{4}-\frac{1}{4}\right)+...+\left(\frac{1}{9}-\frac{1}{9}\right)-\frac{1}{10}\)
\(A=\frac{1}{2}-\frac{1}{10}=\frac{2}{5}\)
CÁCH LÀM NHƯ SAU :
(7/28 + 1/28) + 1/70 + 1/130 + 1/x.(x+3)
8/28 + 1/70 +1/130 +1/x.(x+3)
2/7+1/70+1/130+1/x.(x+3)
(20/70 +1/70)+1/130+1/x.(x+3)
3/10+1/130+1/x.(x+3)
39/130+1/130+1/x.(x+3)
4/13+1/x.(x+3)
Đến đây bn tự làm hộ mình vớ. chúc hok tốt k cho mình nhé
\(\frac{1}{4}+\frac{1}{28}+\frac{1}{70}+\frac{1}{130}+\frac{1}{x\left(x+3\right)}\)
\(=\frac{1}{1.4}+\frac{1}{4.7}+\frac{1}{7.10}+\frac{1}{10.13}+\frac{1}{x\left(x+3\right)}\)
\(=\frac{1}{3}\left(\frac{1}{1}-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}+\frac{1}{x}-\frac{1}{x+3}\right)\)
\(=\frac{1}{3}\left(\frac{1}{1}-\frac{1}{13}+\frac{1}{x}-\frac{1}{x+3}\right)\)
\(=\frac{1}{3}\left(\frac{12}{13}+\frac{1}{x}-\frac{1}{x+3}\right)\)
\(=\frac{1}{3}.\frac{12}{13}+\frac{1}{3}.\frac{1}{x}-\frac{1}{3}.\frac{1}{x+3}\)
\(=\frac{4}{13}+\frac{1}{3x}-\frac{1}{3x+3}\)
\(=\frac{4}{13}+\frac{1}{3x}-\frac{1}{3x+3}\)
\(=\frac{4}{13}+\frac{1}{3x}=\frac{1}{3x+3}\)
\(=\frac{4}{13}+\frac{1}{3x}=\frac{1}{3x+3}\)
\(=\frac{4}{13}+\frac{1}{3x}=\frac{1}{3}.\frac{1}{x+3}\)
\(=\frac{4}{13}=\frac{1}{3}.\frac{1}{x+3}-\frac{1}{3x}\)
\(=\frac{4}{13}=\frac{1}{3}.\frac{1}{x+3}-\frac{1}{3}.\frac{1}{x}\)
\(=\frac{4}{13}=\frac{1}{3}\left(\frac{1}{x+3}-\frac{1}{x}\right)\)
\(=\frac{4}{13}:\frac{1}{3}=\frac{1}{x+1}-\frac{1}{x}\)
\(=\frac{12}{13}=\frac{1}{x+1}-\frac{1}{x}\)
\(=\frac{12}{13}=\frac{x-\left(x+1\right)}{\left(x+1\right)x}\)
\(=\frac{12}{13}=-\frac{1}{x^2+x}\)
\(\Leftrightarrow=12\left(x^2+x\right)=13.\left(-1\right)\)
\(=12\left(x^2+x\right)=-13\)
\(=x^2+x=-\frac{13}{12}\)
\(=x\left(x+1\right)=-\frac{13}{12}\)
.... Chiụ
\(2009-\left(4\frac{5}{9}+x-7\frac{7}{18}\right):15\frac{2}{3}=2008\)
\(2009-\left(\frac{41}{9}+x-\frac{133}{8}\right):\frac{47}{3}=2008\)
\(2009-\left(\frac{41}{9}+x-\frac{133}{8}\right)\times\frac{3}{47}=2008\)
\(2009-\frac{41}{9}\times\frac{3}{47}-x\times\frac{3}{47}+\frac{133}{8}\times\frac{3}{47}=2008\)
\(2009-\frac{41}{141}-x\times\frac{3}{47}+\frac{399}{376}=2008\)
\(2009+(\frac{399}{376}-\frac{41}{141})-x\times\frac{3}{47}=2008\)
\((2009+\frac{869}{1128})-x\times\frac{3}{47}=2008\)
\(x\times\frac{3}{47}=2009+\frac{869}{1128}-2008\)
\(x\times\frac{3}{47}=1\frac{869}{1128}\)
\(x\times\frac{3}{47}=\frac{1997}{1128}\)
\(x=\frac{1997}{1128}:\frac{3}{47}\)
\(x=\frac{1997}{72}\)
\(2009-\left(4\frac{5}{9}+x-7\frac{7}{18}\right):15\frac{2}{3}=\)2008
\(\left(\frac{41}{9}+x-\frac{133}{18}\right):\frac{47}{3}=2009-2008\)
\(\left(\frac{41}{9}+x-\frac{133}{18}\right)=1.\frac{47}{3}=\frac{47}{3}\)
\(\frac{82}{18}+x-\frac{133}{18}=\frac{47}{3}\)
\(x=\frac{282}{18}-\frac{82}{18}+\frac{133}{18}\)
\(x=\frac{333}{18}=\frac{37}{2}\)
Đáp số \(x=\frac{37}{2}\)
xin lỗi bn dấu nhân nó bị trùng với x nên mk thay dấu nhân thành dấu "." theo cách lớp 6 nha.
Nếu có chỗ nào sai thì mk xin lỗi các bạn và mong các bạn góp ý
*****Chúc bạn học giỏi*****
\(=\frac{4}{2x4}+\frac{4}{4x6}+\frac{4}{6x8}+...+\frac{4}{18x20}\)
\(=2\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+...+\frac{1}{18}-\frac{1}{20}\right)\)
\(=2x\left(\frac{1}{2}-\frac{1}{20}\right)\\ =2x\frac{9}{20}\\ =\frac{9}{10}\)
bài 1
a,
32 + 68 :17 x 5 - 29
= 32 + 20 -29
= 52 - 29
= 23
b,
15 x 48 - 30 x 24 - 125
= 720 - 720 -125
= 0-125
a,
32 + 68 :17 x 5 - 29
= 32 + 20 -29
= 52 - 29
= 23
b,
15 x 48 - 30 x 24 - 125
= 720 - 720 -125
= 0-125
\(8\frac{1}{6}:2\frac{1}{2}=\frac{49}{6}:\frac{5}{2}=\frac{98}{30}=\frac{49}{15}\)
\(1\frac{3}{10}:5\frac{7}{8}=\frac{13}{10}:\frac{47}{8}=\frac{104}{470}=\frac{52}{235}\)
Bn như thần ý nhỉ :)
trả lời:
8x1/6:2x1/2
=4/3:1
=4/3
1x3/10:5x7/8
=3/10:35/8
=12/175
chúc học tốt
Ta có: \(M=\frac{1}{21}+\frac{1}{28}+\frac{1}{36}+\frac{1}{45}+\frac{1}{55}\)
\(\Leftrightarrow\frac{1}{2}M=\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}+\frac{1}{110}\)
\(\Leftrightarrow\frac{1}{2}M=\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}+\frac{1}{10.11}\)
\(\Leftrightarrow\frac{1}{2}M=\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+...+\frac{1}{10}-\frac{1}{11}=\frac{1}{6}-\frac{1}{11}=\frac{5}{66}\)
\(\Rightarrow M=\frac{5}{66}:\frac{1}{2}=\frac{5}{33}.\)
\(M=\frac{1}{21}+\frac{1}{28}+\frac{1}{36}+\frac{1}{45}+\frac{1}{55}\)
\(M=\frac{2}{42}+\frac{2}{56}+\frac{2}{72}+\frac{2}{90}+\frac{2}{110}\)
\(M=\frac{2}{6\cdot7}+\frac{2}{7\cdot8}+\frac{2}{8\cdot9}+\frac{2}{9\cdot10}+\frac{2}{10\cdot11}\)
\(M=2\left(\frac{1}{6\cdot7}+\frac{1}{7\cdot8}+\frac{1}{8\cdot9}+\frac{1}{9\cdot10}+\frac{1}{10\cdot11}\right)\)
\(M=2\left(\frac{1}{6}-\frac{1}{11}\right)\)
\(M=2\cdot\frac{5}{66}\)
\(M=\frac{5}{33}\)
Trả lời
2M = \(\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}+\frac{1}{110}\)
= \(\frac{1}{6\cdot7}+\frac{1}{7\cdot8}+\frac{1}{8\cdot9}+\frac{1}{9\cdot10}+\frac{1}{10\cdot11}\)
Bạn tự phân tích tiếp,đến cuối thì chia cho 2
\(M=\frac{1}{21}+\frac{1}{28}+\frac{1}{36}+\frac{1}{45}+\frac{1}{55}\)
\(\frac{1}{2}M=\frac{1}{21\cdot2}+\frac{1}{28\cdot2}+\frac{1}{36\cdot2}+\frac{1}{45\cdot2}+\frac{1}{55\cdot2}\)
\(\frac{1}{2}M=\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}+\frac{1}{110}\)
\(\frac{1}{2}M=\frac{1}{6\cdot7}+\frac{1}{7\cdot8}+\frac{1}{8\cdot9}+\frac{1}{9\cdot10}+\frac{1}{10\cdot11}\)
\(\frac{1}{2}M=\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+...+\frac{1}{10}-\frac{1}{11}\)
\(\frac{1}{2}M=\frac{1}{6}-\frac{1}{11}\)
\(\frac{1}{2}M=\frac{5}{66}\Leftrightarrow M=\frac{5}{33}\)
\(M=\frac{2}{42}+\frac{2}{56}+\frac{2}{72}+\frac{2}{90}+\frac{2}{110}\)
M=2(\(\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}\)\(+\frac{1}{10.11}\)
M=\(2\left(\frac{1}{6}-\frac{1}{11}\right)=2.\frac{5}{66}=\frac{5}{33}\)