(x-31)+7=x-2
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a: =7/8:(2/9-18+1/36)-5/12
=-7/142-5/12=-397/852
b: =3/7(4/9+5/9:6/12)=2/3
c: =5^8(16/31-47/31)+1/3=-5^8+1/3
d: =7/2(3/8+5/8:4/15)=609/64
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a) \(6-\dfrac{2}{5}+\dfrac{3}{5}\) x \(3\)
\(=6-\dfrac{2}{5}+\dfrac{9}{5}\)
\(=\dfrac{30}{5}-\dfrac{2}{5}+\dfrac{9}{5}\)
\(=\dfrac{30-2+9}{5}=\dfrac{37}{5}\)
b) \(\left(\dfrac{31}{35}-\dfrac{4}{7}\right)\) x \(\dfrac{8}{7}:2\)
\(=\left(\dfrac{31}{35}-\dfrac{20}{35}\right)\) x \(\dfrac{8}{7}:2\)
\(=\dfrac{11}{35}\) x \(\dfrac{8}{7}:2\)
\(=\dfrac{11}{35}\) x \(\dfrac{8}{7}\) x \(\dfrac{1}{2}\)
\(=\dfrac{\text{11 x 8 x 1}}{\text{ 35 x 7 x 2}}=\dfrac{88}{490}=\dfrac{88}{245}\)
a) 6−25+356−25+35 x 33
=6−25+95=6−25+95
=305−25+95=305−25+95
=30−2+95=375=30−2+95=375
b) (3135−47)(3135−47) x 87:287:2
=(3135−2035)=(3135−2035) x 87:287:2
=1135=1135 x 8
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A) 7/38 x 9/11 +7/38 x 4/11 -7/38 x 2/11
=7/38.(9/11+4/11-2/11)
=7/38
B) 5/31 x 21/25 + 5/31 x -7/10 - 5/31 x 9/20
=5/31.(21/25-7/10-9/20)
=5/31.(-31/100)
=-1/20
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x - 4 : (6 +7 ) x 2 =31
x - 4 : (13 x 2) = 31
x - 4 : 26 = 31
x : 26= 31 x 4
x : 26 = 124
x=124 : 26
x = 4
t i c k nha
thiếu đè bạn ơi
x - 4 thiếu đây nè (6 +7 ) x 2 =31
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\Rightarrow\)X*(3/5+2/7)=31/70
\(\Rightarrow\)X*31/35=31/70
\(\Rightarrow\)X=31/70:31/35
\(\Rightarrow\)X=1/2
\(x.\frac{3}{5}+x.\frac{2}{7}=\frac{31}{70}\)
\(x.\frac{31}{35}=\frac{31}{70}\)
\(x=\frac{1}{2}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a, (X+7)x8-14=66
=>(X+7)x8=66+14
=>(X+7)x8=80
=>X+7=80:8
=>X+7=10
=>X=10-7
=>X=3
b, 1+2+3+...+X=1711
<=>(X+1)xX:2=1711
=>(X+1)xX=1711x2
=>(X+1)xX=3422=59x58
Vì x<x+1 và (x+1)-x=1
=>x=58
c, X+3/5+Xx2/7=31/70
<=>Xx(1+2/7)+3/5=31/70
=>Xx9/7=31/70-3/5
=>Xx9/7=-11/70
=>X=-11/70:9/7
=>X=-11/90
d, 1/7+6/7xX=1/7
=>6/7xX=1/7-1/7
=>6/7xX=0
=>X=0:6/7
=>X=0
Chúc bạn học giỏi nha!!!
K cho mik với nhé cung bảo bình
Tìm x
\(\dfrac{2}{1\cdot4}x+\dfrac{2}{4\cdot7}x+\dfrac{2}{7\cdot10}x+....+\dfrac{2}{31\cdot34}x=10\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{2}{1.4}x+\dfrac{2}{4.7}x+\dfrac{2}{7.10}x+...+\dfrac{2}{31.34}x=10\)
\(=>1,5.\left(\dfrac{2}{1.4}x+\dfrac{2}{4.7}x+\dfrac{2}{7.10}x+...+\dfrac{2}{31.34}x\right)=15\)
\(=>\dfrac{3}{1.4}x+\dfrac{3}{4.7}x+\dfrac{3}{7.10}x+...+\dfrac{3}{31.34}x=15\)
\(=>x\left(\dfrac{3}{1.4}+\dfrac{3}{4.7}+\dfrac{3}{7.10}+...+\dfrac{3}{31.34}\right)=15\)
\(=>x\left(1-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+...+\dfrac{1}{31}-\dfrac{1}{34}\right)=15\)
\(=>x\left(1-\dfrac{1}{34}\right)=15\)
\(=>\dfrac{33}{34}x=15\)
\(=>x=\dfrac{170}{11}\)