0,75.x -2/5x= 7/20
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a: \(\Leftrightarrow x\cdot\dfrac{3}{5}=\dfrac{-1}{7}+\dfrac{1}{2}=\dfrac{1}{2}-\dfrac{1}{7}=\dfrac{5}{14}\)
\(\Leftrightarrow x=\dfrac{5}{14}:\dfrac{3}{5}=\dfrac{25}{42}\)
b: =>|3x-1|=2
\(\Leftrightarrow\left[{}\begin{matrix}3x-1=2\\3x-1=-2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{1}{3}\end{matrix}\right.\)
c: \(\Leftrightarrow7\left(37-x\right)=3\left(x-13\right)\)
=>259-7x=3x-39
=>-10x=-298
hay x=29,8
d: =>x=3/4+2/3=9/12+8/12=17/12
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câu trả lời đây
- (\(\frac{3}{5}x-0,75\)):\(\frac{3}{7}=\frac{14}{5}\)
- ( \(\frac{3}{5}x-\frac{75}{100}\))\(:\frac{3}{7}=\frac{14}{5}\)
- (\(\frac{3}{5}x-\frac{3}{4}\))\(:\frac{3}{7}=\frac{14}{5}\)
- bí rồi ai giúp mình giải thêm nhé
(3x/5 - 3/4):3/7 =14/5
(3x/5-3/4).7/3 =21x/15 - 21/12 = 14/5
21x =( 14/5 +21/12).15
21x = 273/4
x = 13/4
đã làm là đúng
x =
![](https://rs.olm.vn/images/avt/0.png?1311)
a, \(\Leftrightarrow2x^2=72\)
\(\Leftrightarrow x^2=36\)
\(\Leftrightarrow x=\pm6\)
Vậy ...
\(b,\Leftrightarrow\dfrac{3}{5}x-0,75=2\dfrac{4}{5}.\dfrac{3}{7}=\dfrac{6}{5}\)
\(\Leftrightarrow\dfrac{3}{5}x=\dfrac{6}{5}+0,75=\dfrac{39}{20}\)
\(\Leftrightarrow x=\dfrac{39}{20}:\dfrac{3}{5}=\dfrac{13}{4}\)
Vậy ...
\(c,\Leftrightarrow2x=1\dfrac{5}{6}.\dfrac{6}{11}-\dfrac{3}{10}=\dfrac{7}{10}\)
\(\Leftrightarrow x=\dfrac{7}{10}:2=\dfrac{7}{20}\)
Vậy ...
\(d,\Leftrightarrow\dfrac{1}{x-7\dfrac{1}{3}}=1.5:2\dfrac{1}{4}=\dfrac{2}{3}\)
\(\Leftrightarrow x-7\dfrac{1}{3}=\dfrac{3}{2}\)
\(\Leftrightarrow x=\dfrac{3}{2}+7\dfrac{1}{3}=\dfrac{53}{6}\)
Vậy ...
a) 2x2 - 72 = 0
\(\Rightarrow\) 2x2 = 72
\(\Rightarrow\) x2 = 36 = 62 = (- 6)2
\(\Rightarrow\) x = 6 hoặc x = - 6
Vậy x = 6 hoặc x = - 6
b) (\(\dfrac{3}{5}\)x - 0,75) : \(\dfrac{3}{7}\) = \(2\dfrac{4}{5}\)
\(\Rightarrow\) (\(\dfrac{3}{5}\)x - 0,75) : \(\dfrac{3}{7}\) = \(\dfrac{14}{5}\)
\(\Rightarrow\) \(\dfrac{3}{5}\)x - \(\dfrac{3}{4}\) = \(\dfrac{6}{5}\)
\(\Rightarrow\) \(\dfrac{3}{5}\)x = \(\dfrac{39}{20}\)
\(\Rightarrow\) x = \(\dfrac{13}{4}\)
Vậy x = \(\dfrac{13}{4}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
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a) A = x2( x + y ) - y( x2 + y2 )
= x3 + x2y - x2y - y3
= x3 - y3
Với x = 1 ; y = -1
A = 13 - (-1)3 = 1 + 1 = 2
b) B = 5x( x - 4y ) - 4y( y - 5x )
= 5x2 - 20xy - 4y2 + 20xy
= 5x2 - 4y2
Với x = -0, 6 ; y = -0, 75
B = 5.(-0, 6)2 - 4.(-0, 75)2 = 5.9/25 - 4.9/16 = 9/5 - 9/4 = -9/20
C = x( x - y + 1 ) - y( y + 1 - x )
= x2 - xy + x - y2 - y + xy
= x2 + x - y2 - y
= ( x2 - y2 ) + ( x - y )
= ( x - y )( x + y ) + ( x - y )
= ( x - y )( x + y + 1 )
Thế x = -2/3 ; y = -1/3 ta được
C = [ -2/3 - (-1/3 ) ][ -2/3 - 1/3 + 1 ]
= ( -2/3 + 1/3 ).0
= 0
a, \(A=x^2\left(x+y\right)-y\left(x^2+y^2\right)+2002=x^3-y^3+2002\)
Thay x = 1; y = -1 ta có : \(1^3-\left(-1\right)^3+2002=1-1+2002=2002\)
b, \(5x\left(x-4y\right)-4y\left(y-5x\right)-\frac{11}{20}=5x^2-4y^2-\frac{11}{20}\)
Thay x = -0,6 ; y = -0,75 ta có : \(5.\left(-0,6\right)^2-4\left(-0,75\right)^2-\frac{11}{20}=-1\)
c, \(x\left(x-y+1\right)-y\left(y+1-x\right)=x^2+x-y^2-y\)
Thay x = -2/3 ; y = -1/3 ta có : \(\left(-\frac{2}{3}\right)^2-\frac{2}{3}-\left(-\frac{1}{3}\right)^2+\frac{1}{3}=0\)
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\(\text{a) 5(2x-3)-4(5x-7)=19-2(x+11)}\)
\(10x-15-20x+28=19-2x-22\)
\(10x-20x+2x=19-22-28+15\)
\(-8x=-16\)
\(\Rightarrow x=2\)
\(\text{b) 4(x+3)-7x+17=8(5x-1)+166}\)
\(4x+12-7x+17=40x-8+166\)
\(4x-7x-40x=-8+166-17-12\)
\(-43x=129\)
\(x=-3\)
\(\text{c) 17-14(x+1)=13-4(x+1)-5(x-3)}\)
\(17-14x+14=13-4x-4-5x+15\)
\(-14x+4x+5x=13-4+15-14-17\)
\(-5x=-7\)
\(x=\frac{7}{5}\)
\(\text{d) 5x+3,5+(3x-4)=7x-3(x-0,5)}\)
\(5x+3,5+3x-4=7x-3x+1,5\)
\(5x+3x-7x+3x=1,5-3,5\)
\(x=-2\)
\(\text{e) 7(4x+3)-4(x-1)=15(x+0,75)+7}\)
\(28x+21-4x+4=15x+11,25+7\)
\(28x-4x-15x=11,25+7-4-21\)
\(9x=\frac{-27}{4}\)
\(x=\frac{-3}{4}\)
\(\text{f) 3x+2,42+o,8x=3,38-0,2x}\)
\(3x+0,8x+0,2x=3,38-2,42\)
\(4x=\frac{24}{25}\)
\(x=\frac{6}{25}\)
chúc bạn học tốt !!
![](https://rs.olm.vn/images/avt/0.png?1311)
1) 3x - 6= 5x + 2
5x - 3x = -6 - 2
2x = -8
x = -4
2) 15 - x = 4x - 5
4x + x = 15 + 5
5x = 20
x = 4
Tương tự như trên
0,35x=7/20
x=1
\(0,75.x-\frac{2}{5}.x=\frac{7}{20}\)
=> \(\frac{3}{4}.x-\frac{2}{5}.x=\frac{7}{20}\)
=> \(x\left(\frac{3}{4}-\frac{2}{5}\right)=\frac{7}{20}\)
=> \(x.\frac{7}{20}=\frac{7}{20}\)
=> x=1