7 x 15 = 7 x 5 + 7 x...........
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TK
1
VL
9 tháng 2 2022
6/7 * 5/8*7/3*7/6*8/5
= 6*5*7*7*8 /7*8*3*6*5
=1*1*7*1*1/1*1*3*1*1
= 7/3
19 tháng 3 2023
= 51/20
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= 3/14
------------------------------------
= 4/7 - 2/7
= 2/7
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= 17/45
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= 2/3
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= 2 x 1/4
= 1/2
19 tháng 3 2023
5/9xx6/15=30/135=2/9
4/7:24/5=4/7xx5/24=5/42
6/11:4=6/11xx1/4=3/22
12xx19/18=12/1xx19/18=38/3
15 : 25/4=15/1xx4/25=12/5
1212/1515:2727/2525=1212/1515xx2525/2727=20/27
14/27 : 7/18 x 6/5+3/10=14/27xx18/7xx6/5+3/10=4/3xx6/5+3/10=8/5+3/10=16/10+3/10=19/10
DK
2
28 tháng 12 2016
(15-X)+(X-12)=7-(-5+X)
15-X+X-12=7+5-X
-X+X+X=7+5-15+12
X=9
29 tháng 1
a: \(\dfrac{5}{3}\cdot\dfrac{7}{10}=\dfrac{5}{10}\cdot\dfrac{7}{3}=\dfrac{14}{3}>2\)
\(\dfrac{5}{7}:\dfrac{7}{10}=\dfrac{5}{7}\cdot\dfrac{10}{7}=\dfrac{50}{49}< 2\)
=>\(\dfrac{5}{3}\cdot\dfrac{7}{10}>\dfrac{5}{7}:\dfrac{7}{10}\)
b: \(\dfrac{4}{5}\cdot\dfrac{5}{6}=\dfrac{4}{6}=\dfrac{2}{3}\)
\(\dfrac{8}{9}:\dfrac{4}{3}=\dfrac{8}{9}\cdot\dfrac{3}{4}=\dfrac{8}{4}\cdot\dfrac{3}{9}=\dfrac{2}{3}\)
Do đó: \(\dfrac{4}{5}\cdot\dfrac{5}{6}=\dfrac{8}{9}:\dfrac{4}{3}\)
c: \(\dfrac{5}{11}\cdot\dfrac{33}{15}=\dfrac{5}{15}\cdot\dfrac{33}{11}=\dfrac{3}{3}=1\)
\(\dfrac{6}{17}\cdot\dfrac{34}{25}=\dfrac{34}{17}\cdot\dfrac{6}{25}=2\cdot\dfrac{6}{25}=\dfrac{12}{25}< 1\)
=>\(\dfrac{5}{11}\cdot\dfrac{33}{15}>\dfrac{6}{17}\cdot\dfrac{34}{25}\)
d: \(\dfrac{15}{19}\cdot\dfrac{38}{5}=\dfrac{15}{5}\cdot\dfrac{38}{19}=3\cdot2=6\)
\(\dfrac{15}{16}:\dfrac{3}{8}=\dfrac{15}{16}\cdot\dfrac{8}{3}=\dfrac{15}{3}\cdot\dfrac{8}{16}=\dfrac{5}{2}\)<6
=>\(\dfrac{15}{19}\cdot\dfrac{38}{5}>\dfrac{15}{16}:\dfrac{3}{8}\)
KV
12 tháng 8 2023
a) 3/8 . x = 9/8 - 1
3/8 . x = 1/8
x = 1/8 : 3/8
x = 1/3
b) 4/5 . x = 7/5 - 1/5
4/5 . x = 6/5
x = 6/5 : 4/5
x = 3/2
c) 12/7 : x + 2/3 = 7/5
12/7 : x = 7/5 - 2/3
12/7 : x = 11/15
x = 12/7 : 11/15
x = 180/77
d) 3.(x + 7) - 15 = 27
3.(x + 7) = 27 + 15
3.(x + 7) = 42
x + 7 = 42 : 3
x + 7 = 14
x = 14 - 7
x = 7
T
12 tháng 8 2023
a) \(\dfrac{3}{8}x=\dfrac{9}{8}-1\)
\(\Rightarrow\dfrac{3}{8}x=\dfrac{1}{8}\)
\(\Rightarrow x=\dfrac{1}{8}:\dfrac{3}{8}=\dfrac{1}{3}\)
b) \(\dfrac{4}{5}x=\dfrac{7}{5}-\dfrac{1}{5}\)
\(\Rightarrow\dfrac{4}{5}x=\dfrac{6}{5}\)
\(\Rightarrow x=\dfrac{6}{5}:\dfrac{4}{5}=\dfrac{3}{2}\)
c) \(\dfrac{12}{7}:x+\dfrac{2}{3}=\dfrac{7}{5}\)
\(\Rightarrow\dfrac{12}{7}:x=\dfrac{7}{5}-\dfrac{2}{3}\)
\(\Rightarrow\dfrac{12}{7}:x=\dfrac{11}{15}\)
\(\Rightarrow x=\dfrac{12}{7}:\dfrac{11}{15}=\dfrac{180}{77}\)
d) \(3\left(x+7\right)-15=27\)
\(\Leftrightarrow3\left(x+7\right)=42\)
\(\Leftrightarrow x+7=14\Leftrightarrow x=7\)
K
24 tháng 3 2022
\(a,\dfrac{7}{12}+\dfrac{3}{4}\times\dfrac{2}{9}=\dfrac{7}{12}+\dfrac{1}{6}=\dfrac{7}{12}+\dfrac{2}{12}=\dfrac{9}{12}=\dfrac{3}{4}\)
\(b,\dfrac{8}{9}-\dfrac{4}{15}:\dfrac{2}{5}=\dfrac{8}{9}-\dfrac{4}{15}\times\dfrac{5}{2}=\dfrac{8}{9}-\dfrac{2}{3}=\dfrac{8}{9}-\dfrac{6}{9}=\dfrac{2}{9}\)
NC
15 tháng 8 2020
Bài làm:
Ta có: \(\left(\frac{1}{2}x+\frac{3}{4}\right)^2\div\left(-\frac{3}{14}\right)=-\frac{7}{24}\)
\(\Leftrightarrow\left(\frac{1}{2}x+\frac{3}{4}\right)^2=\frac{1}{16}=\left(\frac{1}{4}\right)^2\)
\(\Leftrightarrow\orbr{\begin{cases}\frac{1}{2}x+\frac{3}{4}=\frac{1}{4}\\\frac{1}{2}x+\frac{3}{4}=-\frac{1}{4}\end{cases}}\Leftrightarrow\orbr{\begin{cases}\frac{1}{2}x=-\frac{1}{2}\\\frac{1}{2}x=-1\end{cases}}\Rightarrow\orbr{\begin{cases}x=-1\\x=-2\end{cases}}\)
15 tháng 8 2020
(\(\frac{1}{2}\).x+\(\frac{3}{4}\))2: \(\frac{-3}{14}\)=\(\frac{-7}{24}\)
(\(\frac{1}{2}\).x+\(\frac{3}{4}\))2 =\(\frac{1}{16}\)
(\(\frac{1}{2}\).x+\(\frac{3}{4}\))2=(\(\frac{1}{4}\))2
\(\hept{\begin{cases}\frac{1}{2}.x+\frac{3}{4}=\frac{1}{4}\\\frac{1}{2}.x+\frac{3}{4}=\frac{-1}{4}\end{cases}}\)<=>\(\hept{\begin{cases}\frac{1}{2}.x=\frac{1}{4}-\frac{3}{4}\\\frac{1}{2}.x=\frac{-1}{4}-\frac{3}{4}\end{cases}}\)<=>\(\hept{\begin{cases}\frac{1}{2}.x=-\frac{1}{2}\\\frac{1}{2}.x=-1\end{cases}}\)
<=>\(\hept{\begin{cases}x=\frac{-1}{2}:\frac{1}{2}=-1\\x=-1:\frac{1}{2}=-2\end{cases}}\)
\(7\times15=7\times5+7\times...\)
\(7\times\left(10+5\right)=7\times5+7\times...\)
\(=7\times10+7\times5=7\times5+7\times....\)
\(=>...=10\)