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a ] mình thấy bạn hình như ghi sai đề
b ] x : [ 25 + 417 ] = 138 = x : 442
x = 442 x 138 = 60996
24 x 36 + 18 x 24 + 18 x 45 - 18 x 7 = 18 x 24 x 2 + 18 x 24 + 18 x 45 - 18 x 7 =
18 x ( 48 + 24 + 45 - 7 ) = 18 x 110 = 1980
\(\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}=\frac{27+9+3+1}{81}=\frac{40}{81}\)
\(\frac{3}{5}< x< \frac{4}{5}\) | \(x=\frac{31}{50}\)
3,5 < x < 3,6 | x = 3,51
\(\frac{7}{4}-x.\frac{3}{4}=\frac{5}{19}\)
\(\Rightarrow1+\frac{3}{4}-x.\frac{3}{4}=\frac{5}{9}\)
\(\Rightarrow\frac{3}{4}.\left(1-x\right)=\frac{5}{9}-1=-\frac{4}{9}\)
\(\Rightarrow1-x=-\frac{4}{9}:\frac{3}{4}=-\frac{16}{27}\)
\(\Rightarrow x=1-\left(-\frac{16}{27}\right)=1+\frac{16}{27}=1\frac{16}{27}\)
1,5 x 3 + 2,5 x 3 + 3,5 x 3 + 4,5 x 5
= 1,5 x 3 + 2,5 x 3 + 3,5 x 3 + 3 x 7,5
= 3 x (1,5 + 2,5 + 3,5 + 7,5)
= 3 x 15
= 45
1,5 x 3 + 2,5 x 3 + 3,5 x 3 + 4,5 x 5
= 1,5 x 3 + 2,5 x 3 + 3,5 x 3 + 3 x 1,5 x 5
= 1,5 x 3 + 2,5 x 3 + 3,5 x 3 + 3 x 7,5
= 3 x ( 1,5 + 2,5 + 3,5 + 7,5 )
= 3 x 15
= 45
\(\dfrac{2}{5}\times\dfrac{1}{7}+\dfrac{2}{7}\times\dfrac{2}{5}\)
\(=\dfrac{2}{5}\times\left(\dfrac{1}{7}+\dfrac{2}{7}\right)\)
\(=\dfrac{2}{5}\times\dfrac{3}{7}\)
\(=\dfrac{6}{35}\)
\(x+\dfrac{1}{2}\times\dfrac{1}{3}=\dfrac{3}{4}\)
\(x+\dfrac{1}{6}=\dfrac{3}{4}\)
\(x=\dfrac{9}{12}-\dfrac{2}{12}\)
\(x=\dfrac{7}{12}\)
\(\left(1-\dfrac{1}{2}\right)\times\left(1-\dfrac{1}{3}\right)\times\left(1-\dfrac{1}{4}\right)\times...\times\left(1-\dfrac{1}{2020}\right)+x=\dfrac{1}{2}\)
\(\dfrac{1}{2}\times\dfrac{2}{3}\times\dfrac{3}{4}\times...\times\dfrac{2019}{2020}+x=\dfrac{1}{2}\)
\(\dfrac{1}{2020}+x=\dfrac{1}{2}\)
\(x=\dfrac{1}{2}-\dfrac{1}{2020}\)
\(x=\dfrac{1010}{2020}-\dfrac{1}{2020}\)
\(x=\dfrac{1009}{2020}\)
\(\dfrac{2}{5}\times\dfrac{1}{7}+\dfrac{2}{7}\times\dfrac{2}{5}\)
\(=\dfrac{2}{5}\times\left(\dfrac{1}{7}+\dfrac{2}{7}\right)\)
\(=\dfrac{2}{5}\times\dfrac{3}{7}\)
\(=\dfrac{6}{35}\)
\(x+\dfrac{1}{2}\times\dfrac{1}{3}=\dfrac{3}{4}\)
\(\Rightarrow\dfrac{1}{2}\times\dfrac{1}{3}=\dfrac{3}{4}-x\)
\(\Rightarrow\dfrac{3}{4}-x=\dfrac{1}{6}\)
\(\Rightarrow x=\dfrac{3}{4}-\dfrac{1}{6}=\dfrac{7}{12}\)
\(\left(1-\dfrac{1}{2}\right)\times\left(1-\dfrac{1}{3}\right)\times\left(1-\dfrac{1}{4}\right)\times...\times\left(1-\dfrac{1}{2020}\right)+x=\dfrac{1}{2}\)
\(\Rightarrow\dfrac{1}{2}\times\dfrac{2}{3}\times\dfrac{3}{4}\times...\times\dfrac{2019}{2020}+x=\dfrac{1}{2}\)
\(\Rightarrow\dfrac{1\times2\times3\times4\times...\times2019}{2\times3\times4\times5\times...\times2020}+x=\dfrac{1}{2}\)
\(\Rightarrow\dfrac{1}{2020}+x=\dfrac{1}{2}\)
\(\Rightarrow x=\dfrac{1}{2}-\dfrac{1}{2020}=\dfrac{1009}{2020}\)
khỏi chép đề nha
a\Câu 1:
200 : ( 15 - x ) = 15 + 5
200 : ( 15 - x ) = 20
15 - x = 200 : 20
15 - x = 10
x = 15 - 10
x = 5
Câu 2:
63 : ( x - 5 ) = 22 -1
63 : ( x - 5 ) = 21
x - 5 = 63 : 21
x - 5 = 3
x = 3 + 5
x = 8
3/4 nhân x - 2/3 = 5/4
3/4 nhân x = 5/4 - 2/3
3/4 nhân x = 3/1
x = 3/4 : 3/1
x = 1/12
3/5 - x = 0,5
3/5 - x = 1/2
x = 3/5 - 1/2
x = 1/10
1,25 nhân x - 3,5 = 1,5
1,25 nhân x = 1,5 + 3,5
1,25 nhân x = 5
x = 1,25 : 5
x = 0,25
x = 1/12
x = 1/10
x = 1/4