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NV
3
DD
15 tháng 10 2017
\(12:y=\frac{3}{4}+\frac{4}{5}\)
\(12:y=\frac{15}{20}+\frac{16}{20}\)
\(12:y=\frac{31}{20}\)
\(y=12:\frac{31}{20}\)
\(y=12x\frac{20}{31}\)
\(y=\frac{240}{31}\)
\(\frac{4}{5}xY=1\)
\(y=1:\frac{4}{5}\)
\(y=1x\frac{5}{4}\)
\(y=\frac{5}{4}\)
\(\frac{37}{63}-y=\frac{1}{7}\)
\(y=\frac{37}{63}-\frac{1}{7}\)
\(y=\frac{37}{63}-\frac{9}{63}\)
\(y=\frac{28}{63}\)
\(y=\frac{4}{9}\)
\(y:\frac{3}{7}=\frac{3}{42}+\frac{5}{7}\)
\(y:\frac{3}{7}=\frac{3}{42}+\frac{30}{42}\)
\(y:\frac{3}{7}=\frac{33}{42}\)
\(y:\frac{3}{7}=\frac{11}{14}\)
\(y=\frac{11}{14}x\frac{3}{7}\)
\(y=\frac{33}{98}\)
LV
15 tháng 10 2017
\(12:y=\frac{3}{4}+\frac{4}{5}\) \(\frac{37}{63}-y=\frac{1}{7}\)
\(12:y=\frac{31}{20}\) \(y=\frac{37}{63}-\frac{1}{7}\)
\(y=12:\frac{31}{20}\) \(y=\frac{4}{9}\)
\(y=\frac{240}{31}\)
\(\frac{4}{5}\cdot y=1\) \(y:\frac{3}{7}=\frac{3}{42}+\frac{5}{7}\)
\(y=1:\frac{4}{5}\) \(y:\frac{3}{7}=\frac{11}{14}\)
\(y=\frac{5}{4}\) \(y=\frac{11}{14}.\frac{3}{7}\)
\(y=\frac{33}{98}\)
PT
1
24 tháng 2 2019
\(\frac{2}{3}+2+\frac{4}{18}=\frac{2}{3}+2+\frac{2}{9}=\frac{6}{9}+\frac{18}{9}+\frac{2}{9}=\frac{6+18+2}{9}=\frac{26}{9}\)\(\frac{26}{9}\)
\(\frac{4}{3}-\frac{2}{5}+\frac{1}{2}=\frac{40}{30}-\frac{12}{30}+\frac{15}{30}=\frac{40-12+15}{30}=\frac{43}{30}\)
\(\frac{1}{72}+\frac{1}{56}+\frac{1}{42}+\frac{1}{30}+\frac{1}{20}+\frac{1}{12}=\)\(\frac{1}{8}-\frac{1}{9}+\frac{1}{7}-\frac{1}{8}+\frac{1}{6}-\frac{1}{7}+\frac{1}{5}-\frac{1}{6}+\frac{1}{4}-\frac{1}{5}+\frac{1}{3}-\frac{1}{4}=\)\(\frac{1}{3}-\frac{1}{9}=\frac{3}{9}-\frac{1}{9}=\frac{3-1}{9}=\frac{2}{9}\)
NT
1. Tính nhanh:
a, 1/1 * 2 + 1/2 * 3 + 1/3 * 4
b, 5/11 *16 + 5/16 * 21 + 5/21 * 26
c, 1/20 + 1/30 + 1/42
1
CD
14 tháng 3 2017
a) 1/1 x 2 + 1/2 x 3 + 1/3 X 4 = 29/6
b) 5/11 x 16 + 5/16 x 21 + 5/21 x 26 = 74015/3696
c) 1/20 +1/30 + 1/42 = 3/28
nho k minh nha
4 tháng 1 2022
Câu 1 :
\(\frac{1}{5}+\frac{3}{5}=\frac{4}{5}\)
\(\frac{15}{105}+\frac{10}{14}=\frac{210}{1470}+\frac{1050}{1470}=\frac{1260}{1470}=\frac{42}{49}\)
23 tháng 8 2019
\(A=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}\)
= \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}\)
= \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\)
= \(1-\frac{1}{7}\)
= \(\frac{7}{7}-\frac{1}{7}\)
= \(\frac{6}{7}\)
2) \(\frac{7}{4}-x.\frac{4}{3}=\frac{5}{19}\)
\(x.\frac{4}{3}=\frac{7}{4}-\frac{5}{19}\)
\(x.\frac{4}{3}=\frac{133}{76}-\frac{20}{76}\)
\(x.\frac{4}{3}=\frac{113}{76}\)
\(x=\frac{113}{76}:\frac{4}{3}\)
\(x=\frac{399}{304}\)
VẬY \(x=\frac{399}{304}\)
b) \(\left(x+\frac{3}{4}\right).\frac{5}{7}=\frac{10}{9}\)
\(\left(x+\frac{3}{4}\right)=\frac{10}{9}:\frac{5}{7}\)
\(x+\frac{3}{4}=\frac{14}{9}\)
\(x=\frac{14}{9}-\frac{3}{4}\)
\(x=\frac{29}{36}\)
Vậy \(x=\frac{29}{36}\)
c) \(x.\frac{1}{2}+\frac{3}{2}.x=\frac{4}{5}\)
\(x.\left(\frac{1}{2}+\frac{3}{2}\right)=\frac{4}{5}\)
\(x.2=\frac{4}{5}\)
\(x=\frac{4}{5}:2\)
\(x=\frac{2}{5}\)
Vậy \(x=\frac{2}{5}\)
Chúc bạn học tốt !!!
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