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a) 60-3(x-2)=51
3(x-2)=60-51
3(x-2)=9
x-2 = 9:3
x-2 = 3
x = 3+2
x 5
a, 128 - 3.( x + 4 ) = 23 b, [( 6x - 39 ) : 7 ] . 4 = 12 c, ( x : 3 - 4 ) . 5 = 15
3. ( x + 4 ) = 128 - 23 [(6x - 39 ) : 7 ] = 3 ( x : 3 - 4 ) = 3
3. ( x + 4 ) = 105 ( 6x - 39 ) = 21 x : 3 = 7
x + 4 = 35 6x = 21 + 39 x = 7 . 3
x = 35 - 4 6x = 60 x = 21
x = 31 x = 10 Vậy x = 21
Vậy x = 31 Vậy x = 10
Trl:
a. 128 - 3 . ( x + 4 ) = 23
=> 3 . ( x + 4 ) = 128 - 23
=> 3 . ( x + 4 ) = 105
=> x + 4 = 105 : 3
=> x + 4 = 35
=> x = 35 - 4
=> x = 31
Vậy x = 31
b. [( 6x - 39 ) : 7 ] . 4 = 12
=> [( 6x - 39 ) : 7 ] = 12 : 4
=> [( 6x - 39 ) : 7 ] = 3
=> ( 6x - 39 ) = 3 . 7
=> ( 6x - 39 ) = 21
=> 6x = 21 + 39
=> 6x = 60
=> x = 60 : 6
=> x = 10
Vậy x = 10
c. ( x : 3 - 4 ) . 5 = 15
=> ( x : 3 - 4 ) = 15 : 5
=> ( x :3 - 4 ) = 3
=> x : 3 = 3 + 4
=> x : 3 = 7
=> x = 7 . 3
=> x = 21
Vậy x = 21
d. | x + 2 | = 0
=> x + 2 = 0
=> x = 0 - 2
=> x = -2
Vậy x = -2
e. | x - 5 | = |-7|
=> | x - 5 | = 7
=> x - 5 = 7 hoặc x - 5 = -7
=> x = 7 + 5 hoặc x = -7 + 5
=> x = 12 hoặc x = -2
Vậy \(x\in\left\{12;-2\right\}\)
a. 3/5 . 15/7 - 15/7 . 8/5
= 15/7(3/5-8/5)
=15/7. -\(\frac{1}{1}\)
=22/7
b. 4/5 . 1 3/7 + 4/5 . 4/7
=4/5(13/7+4/7)
=4/5.17/7
= 68/35
cái chữ này cj nhìn khó hiểu quá nên em thông cảm nếu muốn bt đáp án thì viết rõ ra đc chứ^^
a) 2( x-2) = 8 d) 3x-2x+4=-12
( x-2) = 4 x+4=-12
x = 6 x=-16
b ) 3( x-2)=-6 e) -3x+x-4=-14
(x-2)=-2 -2x-4=-14
x = 0 -2x=-10
c) 4(3-x)=-24 x=5
3-x=6 f) 2(x-2)-x+25=-7
x=-3 2x-4-x+25=-7
x+21=-7
x=-28
g) - 12 x + 60 + 21 - 7 x = 5 h) x - 2=0 suy ra x=2
-19 x +81 =5 x-4=0 suy ra x=4
-19x = - 76 vậy x = 2 và x = 4
x = 4
i) x - 2 = 0 suy ra x = 2
x + 15 = 0 suy ra x = - 15
vậy x = 2 và x = -15
~ chúc bn học tốt ~ # Q.Trang#
Bài 1:
\(\frac{3}{5}+\frac{4}{15}=\frac{9}{15}+\frac{4}{15}=\frac{13}{15}\)
\(\frac{5}{6}:\frac{-7}{12}=\frac{5}{6}.\frac{-12}{7}=\frac{-60}{42}=\frac{-10}{7}\)
\(\frac{-21}{24}:\frac{-14}{8}=\frac{-21}{24}.\frac{-8}{14}=\frac{168}{336}=\frac{1}{2}\)
\(\frac{4}{5}:\frac{-8}{15}=\frac{4}{5}.\frac{-15}{8}=\frac{-60}{40}=\frac{-3}{2}\)
\(\frac{5}{12}-\frac{-7}{6}=\frac{5}{12}+\frac{7}{6}=\frac{5}{12}+\frac{14}{12}=\frac{19}{12}\)
\(\frac{-15}{16}.\frac{8}{25}=\frac{-120}{400}=\frac{-3}{10}\)
Bài 2 :
\(6\frac{4}{5}-\left(1\frac{2}{3}+3\frac{4}{5}\right)\)
\(=\frac{34}{5}-\left(\frac{5}{3}+\frac{19}{5}\right)\)
\(=\frac{34}{5}-\frac{5}{3}-\frac{19}{5}\)
\(=\left(\frac{34}{5}-\frac{19}{5}\right)-\frac{5}{3}\)
\(=3-\frac{5}{3}\)
\(=\frac{4}{3}\)
\(6\frac{5}{7}-\left(1\frac{2}{3}+2\frac{5}{7}\right)\)
\(=\frac{47}{7}-\left(\frac{5}{3}+\frac{19}{7}\right)\)
\(=\frac{47}{7}-\frac{5}{3}-\frac{19}{7}\)
\(=\left(\frac{47}{7}-\frac{19}{7}\right)-\frac{5}{3}\)
\(=4-\frac{5}{3}\)
\(=\frac{7}{3}\)
\(\frac{4}{19}.\frac{-3}{7}+\frac{-3}{7}.\frac{15}{19}+\frac{5}{7}\)
\(=\left(\frac{4}{19}+\frac{15}{19}\right).\frac{-3}{7}+\frac{5}{7}\)
\(=1.\frac{-3}{7}+\frac{5}{7}\)
\(=\frac{-3}{7}+\frac{5}{7}\)
\(=\frac{2}{7}\)
\(\frac{5}{9}.\frac{7}{13}+\frac{5}{9}.\frac{9}{13}-\frac{5}{9}.\frac{3}{13}\)
\(=\frac{5}{9}.\left(\frac{7}{13}+\frac{9}{13}-\frac{3}{13}\right)\)
\(=\frac{5}{9}.1\)
\(=\frac{5}{9}\)
a, Ta có : \(x-5=-1\)
\(\Leftrightarrow x=\left(-1\right)+5\)
\(\Rightarrow x=4\)
Vậy \(x=4\)
b, Ta có :\(x+30=-4\)
\(\Leftrightarrow\left(-4\right)-30\)
\(\Leftrightarrow x=\left(-34\right)\)
Vậy \(x=\left(-34\right)\)
c, Ta có : \(x-\left(-24\right)=3\)
\(x=3+\left(-24\right)\)
\(\Leftrightarrow x=\left(-21\right)\)
Vậy \(x=\left(-21\right)\)
d,Ta có : \(22-\left(-x\right)=12\)
\(\Leftrightarrow\left(-x\right)=22-12\)
\(\Leftrightarrow\left(-x\right)=10\)
Vậy ....
a)25+(`15-x)=30
15-x=25-30
x=15-5
x=10
b)43-(24-x)=20
24-x=43-20
x=24-23
x=1
c)2.(x-50-17=25
2.(x-5)=25+17
x-5=42:2
x=21+5
x=26
d)3.(x+7)-15=27
3.(x+7)=15+27
x+7=42:3
x=14-7
x=7
a . 13-|x+5|=14
\(\Rightarrow Ix+5I=-1\)
\(\Rightarrow x\in\varnothing\)
b.27-3 | x-2|=15
\(3Ix-2I=12\)
\(|x-2|=4\)
\(\Rightarrow\orbr{\begin{cases}x-2=4\\x-2=-4\end{cases}\Leftrightarrow\orbr{\begin{cases}x=6\\x=-2\end{cases}}}\)
c 10+|x-15|=3
\(Ix-15I=-7\)
\(\Rightarrow x\in\varnothing\)
2 Tìm số nguyên a sao cho
a -32 (a+21)=0
\(a+21=0\)
\(a=-21\)
b (a+1) (a-2)=0
\(\Rightarrow\orbr{\begin{cases}a+1=0\\a+2=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=-1\\a=-2\end{cases}}}\)
c 15+a^2=24
\(a^2=9\)
\(a=\pm3\)
học tốt
Đáp án là B