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1. a
\(\dfrac{8}{5}-\dfrac{5}{6}\cdot\dfrac{3}{4}\)
\(=\dfrac{8}{5}-\dfrac{5\cdot3}{3\cdot2\cdot4}\)
\(=\dfrac{8}{5}-\dfrac{5}{8}=\dfrac{39}{40}\)
1.b
\(=\dfrac{7}{8}+\dfrac{5}{6}\cdot\dfrac{3}{2}\)
\(=\dfrac{7}{8}+\dfrac{5\cdot3}{3\cdot2\cdot2}\)
\(=\dfrac{7}{8}+\dfrac{5}{4}=\dfrac{17}{8}\)
2.a
\(\dfrac{4}{5}+x=\dfrac{11}{10}\)
\(x=\dfrac{11}{10}-\dfrac{4}{5}=\dfrac{3}{10}\)
2.b
\(x-\dfrac{3}{4}=\dfrac{5}{7}\)
\(x=\dfrac{5}{7}+\dfrac{3}{4}=\dfrac{41}{28}\)
ta có \(\frac{x}{3}=\frac{y}{8}=\frac{z}{5}\)
=> \(\frac{3x}{9}=\frac{y}{8}=\frac{z}{5}=\frac{3x+y-z}{9+8-5}=\frac{14}{12}=\frac{7}{6}\)
=> \(\frac{x}{3}=\frac{y}{8}=\frac{z}{5}\)\(=\frac{7}{6}\)
=> \(x\)\(=\frac{7\cdot3}{6}=\frac{21}{6}=\frac{7}{2}\)
=> \(y=\frac{7\cdot8}{6}=\frac{56}{6}\)
=>\(z=\frac{7\cdot5}{6}=\frac{35}{6}\)
số xấu vậy em
a/ 6/5 < x < 28/8
=> 1 < x < 4
=> x thuộc { 2 ; 3}
Vậy x thuộc { 2 ; 3}
b/ x < 5/7 < y
=> x < 1; 0 < y
=> x = 0; y = 1
Vậy x = 0, y = 1
1) a) \(\frac{5454}{5757}-\frac{171717}{191919}=\frac{18\times3\times101}{19\times3\times101}-\frac{17\times10101}{19\times10101}=\frac{18}{19}-\frac{17}{19}=\frac{1}{19}\)
b) \(\frac{6}{5}\times\frac{7}{6}\times\frac{8}{7}\times....\times\frac{2021}{2020}=\frac{6\times7\times8\times...\times2021}{5\times6\times7\times...\times2020}=\frac{2021}{5}\)
2) \(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{1}{45}=2\times\frac{1}{6}+2\times\frac{1}{12}+2\times\frac{1}{20}+...+2\times\frac{1}{90}\)
\(=2\times\left(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}\right)\)
\(=2\times\left(\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+...+\frac{1}{9\times10}\right)\)
\(=2\times\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{9}-\frac{1}{10}\right)=2\times\left(\frac{1}{2}-\frac{1}{10}\right)=2\times\frac{2}{5}=\frac{4}{5}\)
b)Vì \(a-1< a+1\)
=> \(\frac{1}{a-1}>\frac{1}{a+1}\)
\(3-\left(\frac{43}{8}+x-\frac{173}{24}\right):\frac{50}{3}=2\)
\(3-\left(\frac{43}{8}+x-\frac{173}{24}\right)=2×\frac{50}{3}\)
\(3-\left(\frac{43}{8}+x-\frac{173}{24}\right)=\frac{100}{3}\)
\(\left(\frac{43}{8}+x-\frac{173}{24}\right)=3-\frac{100}{3}\)
\(\left(\frac{43}{8}+x-\frac{173}{24}\right)=-\frac{91}{3}\)
\(\frac{43}{8}+x=-\frac{91}{3}+\frac{173}{24}\)
\(\frac{43}{8}+x=-\frac{185}{8}\)
\(x=-\frac{185}{8}-\frac{43}{8}\)
\(x=-\frac{57}{2}\)
vậy \(x=-\frac{57}{2}\)
nhầm
\(3-\left(\frac{43}{8}+x-\frac{173}{24}\right):\frac{50}{3}=2\)
\(\left(\frac{43}{8}+x-\frac{173}{24}\right):\frac{50}{3}=3-2\)
\(\left(\frac{43}{8}+x-\frac{173}{24}\right):\frac{50}{3}=1\)
\(\left(\frac{43}{8}+x-\frac{173}{24}\right)=1×\frac{50}{3}\)
\(\left(\frac{43}{8}+x-\frac{173}{24}\right)=\frac{50}{3}\)
\(\frac{43}{8}+x=\frac{50}{3}+\frac{173}{24}\)
\(\frac{43}{8}+x=\frac{191}{8}\)
\(x=\frac{191}{8}-\frac{43}{8}\)
\(x=\frac{37}{2}\)
vậy \(x=\frac{37}{2}\)
a, 3/4 ÷ x/6 = 0,75
x/6 = 0,75 ÷ 0,75
x/6 = 1
=> x = 6
Vậy x = 6
b, 2,5 . 45/ x = 5/6
45/x = 5/6 ÷ 2,5
45/x = 1/3
=> x = 45 × 3
=> x = 135
Vậy x = 135
c, x/12 + 121,5 = 121,5
x/12 = 121,5 - 121,5
x/12 = 0
=> x = 0
Vậy x = 0
e, 6/8 = 15/x
3/4 = 15/x
=> x = 20
Vậy x = 20
1.
7/15:(1/2-9/10xX)-1/6=13/6
=>7/15:(1/2-9/10xX)=13/6+1/6
=>7/16:(1/2-9/10xX)=7/3
=>1/2-9/10xX=7/16:7/3
=>1/2-9/10xX=3/16
=>9/10xX=1/2-3/16
=>9/10xX=5/16
=>X=5/16:9/10
=>X=25/72
- Tính giá trị biểu thức:
a) (2/5 x 25/29) + (3/5 x 25/29)
= (50/145) + (75/145)
= 125/145
b) (5/2 x 3/7) - (3/14 : 6/7)
= 15/14 - (3/14 x 7/6)
= 15/14 - 1/2
= (30/28) - (14/28)
= 16/28
= 4/7
c) (15/4 : 5/12) - (6/5 : 11/15)
= (15/4 x 12/5) - (6/5 x 15/11)
= 180/20 - 90/55
= 9 - 18/11
= (99/11) - (18/11)
= 81/11
= 7 4/11
- Tính giá trị biểu thức:
a) (2/3) + (20/21 x 3/2 x 7/5)
= 2/3 + (60/210)
= 2/3 + 2/7
= (14/21) + (6/21)
= 20/21
b) (5/17 x 21/32 x 47/24 x 0)
= 0
c) (11/3 x 26/7) - (26/7 x 8/3)
= (286/21) - (208/21)
= 78/21
= 3 9/21
= 3 3/7
- Tìm x:
a) (25/8) : x = 5/16
=> (25/8) x (16/5) = x
=> 4 = x
b) x + (7/15) = 6/15
=> x = (6/15) - (7/15)
=> x = -1/15
c) x : (28/49) = 7/12
=> x x (49/28) = 7/12
=> x = (7/12) x (28/49)
=> x = 1/2
- Tìm x:
a) 6 x x = (5/8) : (3/4)
=> 6x = (5/8) x (4/3)
=> 6x = 20/24
=> 6x = 5/6
=> x = (5/6) / 6
=> x = 5/36
câu,b,không,đủ,thông,tin,nhan,bạn.
\(\dfrac{x}{2}=\dfrac{7}{y}=\dfrac{28}{8}\\ =>\left\{{}\begin{matrix}\dfrac{x}{2}=\dfrac{28}{8}\\\dfrac{7}{y}=\dfrac{28}{8}\end{matrix}\right.=>\left\{{}\begin{matrix}x=\dfrac{28.2}{8}\\y=\dfrac{7.8}{28}\end{matrix}\right.=>\left\{{}\begin{matrix}x=7\\y=2\end{matrix}\right.\)
x = 7
y = 2