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a) 2(x + 15) - 7 - x = 15 + 2x
2x + 30 - 7 - x = 15 + 2x
2x - x - 2x = 15 - 30 + 7
-x = -8
x = 8
b) - (x + 7) + 2(5 - x) = 4x + 15
-x - 7 + 10 - 2x = 4x + 15
0x = 19
Vậy phương trình vô nghiệm
a) 2( x + 15 ) - 7 - x = 15 + 2x
=> 2( x + 15 ) - 7 - x - 15 - 2x = 0
=> 2x + 30 - 7 - x - 15 - 2x = 0
=> -x + 8 = 0
=> -x =- 8
=> x = 8
b) - ( x + 7 ) + 2( 5 -x ) = 4x + 15
=> - x - 7 + 10 - 2x - 4x - 15 = 0
=> -7x - 12 = 0
=> -7x = 12
=> \(x=-\frac{12}{7}\)
`1, -2/9 xx 15/17 + (-2/9) xx 2/17`
`= -2/9 xx (15/17 + 2/17)`
`= -2/9 xx 17/17`
`=-2/9xx1`
`=-2/9`
__
`-5/3 xx 6/5 + (-7/9) xx 3/10`
`= -30/15 + (-21/90)`
`= -2 + (-7/30)`
`=-60/30 +(-7/30)`
`=-67/30`
__
`15/20 xx 7/5 + (-9/7) xx (-6/4)`
`=3/4 xx7/5 + (-9/7) xx(-6/4)`
`= 21/20 + 54/28`
`= 21/20 + 27/14`
`=417/140`
__
`-25/13 xx 5/19 + (-25/13) xx 14/19`
`=-25/13 xx (5/19 +14/19)`
`=-25/13 xx 19/19`
`= -25/13 xx 1`
`=-25/13`
__
`-7/13 xx 13/5 + (-9/7) xx 5/3`
`=-7/5 +(-15/7)`
`=-124/35`
b: =>x(8-7)=-33
=>x=-33
c: =>-12x+60+21-7x=5
=>-19x=-76
hay x=4
d: =>-2x-2-x+5+2x=0
=>3-x=0
hay x=3
a: \(A=\dfrac{-7}{28}\cdot\dfrac{15}{25}=\dfrac{-1}{4}\cdot\dfrac{3}{5}=\dfrac{-3}{20}\)
b: \(B=\dfrac{-5\cdot7}{14\cdot\left(-3\right)}=\dfrac{35}{42}=\dfrac{5}{6}\)
c: \(C=\dfrac{-1}{5}-\dfrac{1}{5}\cdot\dfrac{3}{5}=\dfrac{-1}{5}-\dfrac{3}{25}=\dfrac{-8}{25}\)
d: \(D=\dfrac{-3}{4}-\dfrac{1}{4}=-1\)
e: \(E=\dfrac{-4}{5}\left(1-\dfrac{15}{16}\right)=\dfrac{-4}{5}\cdot\dfrac{1}{16}=\dfrac{-1}{20}\)
f: \(F=\dfrac{6-7}{4}\cdot\dfrac{4+12}{22}=\dfrac{-1}{4}\cdot\dfrac{8}{11}=\dfrac{-2}{11}\)
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
a) \(x-2=-6\)
\(x=-6+2\)
\(x=-4\)
2) \(-5x-\left(-3\right)=13\)
\(-5x+3=13\)
\(-5x=13-3\)
\(-5x=10\)
\(x=-2\)
3) \(15-\left(x-7\right)=-21\)
\(15-x+7=-21\)
\(22-x=-21\)
\(x=22+21\)
\(x=43\)
b) \(2x-\left(-17\right)=15\)
\(2x+17=15\)
\(2x=15-17\)
\(2x=-2\)
\(x=-1\)
5) \(\left|x-3\right|-7=13\)
\(\left|x-3\right|=20\)
\(\Rightarrow\orbr{\begin{cases}x-3=20\\x-3=-20\end{cases}}\Rightarrow\orbr{\begin{cases}x=23\\x=-17\end{cases}}\)
15-x=7-(-2)
15-x=9
x=15-9
x=6
15-x=7-(-2)
15-x=9
x=15-9
x=6