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(2+x)+(4+x)+...+(52+x)=780
=>(x+x+...+x)+(2+4+...+52)=780
=>26x+702=780
=>26x=78
=>x=3
=>(2+4+...+52)+(x+x+...+x)=780 (26 số hạng x)
=>(52+2).26/2+26x=780
=>702+26x=780
=>26x=780-702
=>26x=78
=>x=78:26
=>x=3
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![](https://rs.olm.vn/images/avt/0.png?1311)
6\(^2\)+ 64 : ( x - 1 ) = 52
36 + 64 : ( x - 1 ) =52
64 ; ( x - 1 ) =64 : 52
x - 1 = \(\frac{16}{13}\)
x = \(\frac{16}{13}\)+1
x = \(\frac{29}{13}\)
HT
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Câu 1:
[(4x+28).3+5.5]:5=35
[(4x+28).3+5.5]=35.5
(4x+28).3+25=175
(4x+28).3=175-25
(4x+28).3=150
4x+28=150:3
4x+28=50
4x=50-28
4x=22
x=22:4
x=5,5
a.\([\)(4x+28).3+5.5\(]\):5=35\(\Leftrightarrow\)4(x+7).3+25=175\(\Leftrightarrow\)4(x+7).3=150\(\Leftrightarrow\)4.(x+7)=50\(\Leftrightarrow\)x+7=\(\frac{25}{2}\)\(\Leftrightarrow\)x=\(\frac{11}{2}\)
b.720:\([\)41-(2x-5)\(]\)=40\(\Leftrightarrow\)41-(2x-5)=18\(\Leftrightarrow\)2x-5=23\(\Leftrightarrow\)x=14
c.3x+8x-30=25\(\Leftrightarrow\)11x=55\(\Leftrightarrow\)x=5
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Answer:
Bài 3:
\(334-\left(-75\right)+[\left(-175\right)-34]\)
\(=334+75-175-34\)
\(=\left(334-34\right)+\left(75-175\right)\)
\(=300+\left(-100\right)\)
\(=200\)
\(68-\left(-45\right)-[368-\left(-145\right)]\)
\(=68+45-[368+145]\)
\(=\left(68-368\right)+\left(45-145\right)\)
\(=\left(-300\right)+\left(-100\right)\)
\(=-400\)
Bài 4:
\(-17-\left(x-5\right)=-52\)
\(\Rightarrow x-5=-17-\left(-52\right)\)
\(\Rightarrow x-5=35\)
\(\Rightarrow x=40\)
\(3\left(7-x\right)+\left(-12\right)=-75\)
\(\Rightarrow3\left(7-x\right)=-75-\left(-12\right)\)
\(\Rightarrow3\left(7-x\right)=-63\)
\(\Rightarrow7-x=-21\)
\(\Rightarrow x=28\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có : \(\frac{x+5}{4}=\frac{x-4}{3}\)
\(\Rightarrow3\left(x+5\right)=4\left(x-4\right)\)
\(\Leftrightarrow3x+15=4x-16\)
\(\Leftrightarrow3x-4x=-16-15\)
\(\Leftrightarrow-x=-31\)
\(\Rightarrow x=31\)
`52 -4(x- 5) = 40`
`4(x-5) = 52-40 =12`
`x-5 = 12/4=3`
`x=3+5=8`
Vậy `x=8`
x=8