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câu 1:
a 3/11 - 7/11 + 2/11 = 3 - 7 + 2 / 11
= -5 + 2/11
= -3/11
b 7/15 - 2/3 = 7/15 - 10/15
= -1/5
c 3/5.9/11 + 3/5.2/11 - 2 1/2
= 3/5.9/11 + 3/5.2/11 - 5/2
= 3/5.( 9/11 + 2/11 - 5/2 )
= 3/5.( 1 - 5/2 )
= 3/5 . -3/2
= -9/10
câu 2
a. x + 75% = 5/12
x + 3/4 = 5/12
x = 5/12 - 3/4
x = -1/3
vậy x = -1/3
b.| x - 7/15 | = 3/10
x - 7/15 = 3/10 => x = 3/10 + 7/15 => x = 23/30
x - 7/15 = -3/10 => x = -3/10 + 7/15 => x = 1/6
vậy x = 23/30 hoặc 1/6
tk mk nhé mk làm đc nửa bài rùi
Câu 1 :
a) \(\frac{3}{11}-\frac{7}{11}+\frac{2}{11}=\frac{-4}{11}+\frac{2}{11}=\frac{-2}{11}\)
b) \(\frac{7}{15}+\frac{2}{3}=\frac{7}{15}+\frac{10}{15}=\frac{17}{15}\)
c) \(\frac{3}{5}.\frac{9}{11}+\frac{3}{5}.\frac{2}{11}-2\frac{1}{2}\)
\(=\left(\frac{3}{5}.\frac{9}{11}+\frac{3}{5}.\frac{2}{11}\right)-\frac{5}{2}\)
\(=\frac{3}{5}.\left(\frac{9}{11}+\frac{2}{11}\right)-\frac{5}{2}\)
\(=\frac{3}{5}.1-\frac{5}{2}\)
\(=\frac{3}{5}-\frac{5}{2}=\frac{6}{10}-\frac{25}{10}=\frac{-19}{10}=-1\frac{9}{10}\)
Câu 2 :
a) \(x+75\%=\frac{5}{12}\)
\(x+\frac{3}{4}=\frac{5}{12}\)
\(x=\frac{5}{12}-\frac{3}{4}\)
\(x=\frac{5}{12}-\frac{9}{12}=\frac{-4}{12}=\frac{-1}{3}\)
Vậy : \(x=\frac{-1}{3}\)
Câu 3 :
Giải :
Số HS trung bình là :
\(48.\frac{5}{12}=20\left(HS\right)\)
Số HS còn lại là :
\(48-20=28\)\(\left(HS\right)\)
Số HS khá là :
\(28.\frac{4}{7}=16\left(HS\right)\)
Số HS giỏi là :
\(28-16=12\left(HS\right)\)
Đ/S : 12 Học sinh
Bài 1 : Tính :
a, \(-\frac{8}{3}.\frac{6}{13}.\frac{7}{13}.\frac{-3}{8}+1\frac{3}{8}\)
\(=\left(-\frac{8}{3}.-\frac{3}{8}\right).\left(\frac{6}{13}.\frac{7}{13}\right)+1\frac{3}{8}\)
\(=1.\frac{42}{169}+1\frac{3}{8}\)
\(=\frac{2195}{1352}\)
b) \(75\%-\left(\frac{5}{2}+\frac{5}{3}\right)+\left(-\frac{1}{2}\right)^2\)
\(=\frac{3}{4}-\frac{25}{6}+\frac{1}{4}\)
\(=\frac{3}{4}+\frac{1}{4}-\frac{25}{6}\)
\(=1-\frac{25}{6}\)
\(=-\frac{19}{6}\)
~Hok tốt~
Bài 2 :
a)\(\frac{3}{5}.x-\frac{2}{3}=\frac{1}{2}\) b) \(\left(\frac{1}{2}-x\right).\frac{2}{3}=\frac{1}{8}\)
\(\frac{3}{5}.x=\frac{1}{2}+\frac{2}{3}\) \(\frac{1}{2}-x=\frac{1}{8}:\frac{2}{3}\)
\(\frac{3}{5}.x=\frac{7}{6}\) \(\frac{1}{2}-x=\frac{3}{16}\)
\(x=\frac{7}{6}:\frac{3}{5}\) \(x=\frac{1}{2}-\frac{3}{16}\)
\(x=\frac{35}{18}\) \(x=\frac{5}{16}\)
c) \(\left|2x-\frac{3}{7}\right|-\frac{1}{2}=\frac{3}{4}\)
\(\left|2x-\frac{3}{7}\right|=\frac{3}{4}+\frac{1}{2}\)
\(\left|2x-\frac{3}{7}\right|=\frac{5}{4}\)
\(\Rightarrow2x-\frac{3}{7}\in\left\{\frac{5}{4};-\frac{5}{4}\right\}\)
\(TH1:2x-\frac{3}{7}=\frac{5}{4}\) \(TH2:2x-\frac{3}{7}=-\frac{5}{4}\)
\(\Rightarrow2x=\frac{5}{4}+\frac{3}{7}\) \(\Rightarrow2x=-\frac{5}{4}+\frac{3}{7}\)
\(2x=\frac{47}{28}\) \(2x=-\frac{23}{28}\)
\(x=\frac{47}{28}:2\) \(2x=-\frac{23}{28}:2\)
\(x=\frac{47}{56}\) \(2x=-\frac{23}{56}\)
\(\Rightarrow x\in\left\{\frac{47}{56};-\frac{23}{56}\right\}\)
Bài làm
a) \(-\frac{3}{7}+\frac{3}{4}:\frac{3}{14}\)
= \(-\frac{3}{7}+\frac{3}{4}.\frac{14}{3}\)
= \(-\frac{3}{7}+\frac{7}{2}\)
\(=-\frac{7}{14}+\frac{49}{14}\)
\(=\frac{42}{14}=3\)
b) \(5-\frac{7}{39}:\frac{7}{13}+\frac{8}{9}:4\)
\(=5=\frac{7}{39}.\frac{13}{7}+\frac{8}{9}.\frac{1}{4}\)
\(=5-\frac{1}{3}+\frac{2}{9}\)
\(=\frac{45}{9}-\frac{3}{9}+\frac{2}{9}\)
\(=\frac{44}{9}\)
c) \(\left(\frac{5}{12}:\frac{11}{6}+\frac{5}{12}:\frac{11}{5}\right)-\frac{-7}{12}\)
\(=\left(\frac{5}{12}.\frac{6}{11}+\frac{5}{12}.\frac{5}{11}\right)+\frac{7}{12}\)
\(=\left[\frac{5}{12}\left(\frac{6}{11}+\frac{5}{11}\right)\right]+\frac{7}{12}\)
\(=\frac{5}{12}+\frac{7}{12}\)
\(=\frac{12}{12}=1\)
d) \(-\frac{5}{9}+\frac{14}{9}\left(\frac{3}{4}-\frac{2}{5}\right):49\)
\(=-\frac{5}{9}+\frac{14}{9}\left(\frac{15}{20}-\frac{8}{20}\right):49\)
\(=-\frac{5}{9}+\frac{14}{9}.\frac{7}{20}.\frac{1}{49}\)
\(=-\frac{5}{9}+\frac{7}{9}.\frac{7}{10}.\frac{1}{7.7}\)
\(=-\frac{5}{9}+\frac{1}{90}\)
\(=-\frac{50}{90}+\frac{1}{90}=-\frac{49}{90}\)
a) A = \(\frac{\frac{3}{5}+\frac{3}{7}-\frac{3}{11}}{\frac{4}{5}+\frac{4}{7}+\frac{4}{41}}\)= \(\frac{\frac{21}{35}+\frac{15}{35}-\frac{3}{11}}{\frac{28}{35}+\frac{20}{35}+\frac{4}{41}}\)= \(\frac{\frac{36}{35}-\frac{3}{11}}{\frac{48}{35}+\frac{4}{41}}\)= \(\frac{\frac{36}{35}-\frac{36}{132}}{\frac{48}{35}+\frac{48}{492}}\)
Từ đây bạn tự làm nha
b) \(\frac{-1}{2}+\frac{-2}{2}+\frac{-3}{4}\)
= \(\frac{-3}{2}\)+ \(\frac{-3}{4}\)
= \(\frac{-6}{4}\)+ \(\frac{-3}{4}\)
= \(\frac{-9}{4}\)
Dài quá mình làm 2 bài này thôi
Bài 1 câu c làm tương tự câu a
Bạn đăng lên nhiều bài quá làm đến đêm mất
Có khi làm đến đêm còn chưa xong nữa là
Bạn đăng lần lượt thôi chứ
Bài 1:
a,\(\frac{3.21}{14.15}\)=\(\frac{1.3}{2.5}\)=\(\frac{3}{10}\)
b,\(\frac{49+7.49}{49}\)=\(\frac{49\left(7+1\right)}{49}\)=\(\frac{1.8}{1}\)=8