Tính
a) (4,578 x 3 + 5,422 x 3 ) : 1,2 - 1,2
b) 3/5 x 9/7 - 3/5 x 3/14
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a; 60 \(\times\) (\(\dfrac{7}{12}\) + \(\dfrac{4}{15}\))
= 60 \(\times\) \(\dfrac{7}{12}\) + 60 \(\times\) \(\dfrac{4}{15}\)
= 35 + 16
= 51
a,\(60\times\left(\frac{7}{12}+\frac{4}{15}\right)\)\(=\frac{60\times7}{12}+\frac{60\times4}{15}\)
\(=\frac{12\times5\times7}{12}+\frac{15\times4\times4}{15}\)
\(=5\times7+4\times4\)
\(=35+16\)
\(=51\)
b, \(\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times...\times\frac{8}{9}\)\(=\frac{1\times2\times3\times4\times5\times6\times7\times8}{2\times3\times4\times5\times6\times7\times8\times9}\)
\(=\frac{1}{9}\)
`3/7xx14/5+32/5xx3/7+3/7xx9/5`
`=3/7xx(14/5+32/5+9/5)`
`=3/7xx55/5`
`=3/7xx5`
`=15/7`
\(=\frac{3}{7}\times[\frac{14}{5}+\frac{32}{5}+\frac{9}{5}]=\frac{3}{7}\times\frac{55}{5}=\frac{3}{7}\times11=\frac{33}{7}\)
\(2\left(x-5\right)+3\left(2-3x\right)=5x+7\)
\(\Leftrightarrow2x-10+6-9x=5x+7\)
\(\Leftrightarrow\left(2x-9x\right)+\left(6-10\right)=5x+7\)
\(\Leftrightarrow-7x-4=5x+7\)
\(\Leftrightarrow-7x-5x=4+7\)
\(\Leftrightarrow-12x=11\)
\(\Leftrightarrow x=\frac{-11}{12}\)
\(3x-5\left(x-2\right)+7=4x-12\)
\(\Leftrightarrow3x-5x-10+7=4x-12\)
\(\Leftrightarrow\left(3x-5x\right)-\left(10-7\right)=4x-12\)
\(\Leftrightarrow-2x-3=4x-12\)
\(\Leftrightarrow-2x-4x=3-12\)
\(\Leftrightarrow-6x=-15\)
\(\Leftrightarrow x=\frac{-15}{-6}=\frac{5}{2}\)
\(\text{n) 3-|2x-1|=(-5)}\)
\(\Rightarrow\left|2x-1\right|=3-\left(-5\right)=8\)
\(\Rightarrow\orbr{\begin{cases}2x-1=8\\2x-1=-8\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{9}{2}\\x=-\frac{7}{2}\end{cases}}}\)
\(\text{o) 12+|3-x|=9}\)
\(\Rightarrow\left|3-x\right|=9-12\)
\(\Rightarrow\left|3-x\right|=-3\)
\(\Rightarrow\text{Phương trình vô nghiệm }\)
\(\text{p) |x+9|=12+(-9)+2}\)
\(\Rightarrow\left|x+9\right|=5\)
\(\Rightarrow\orbr{\begin{cases}x+9=5\\x+9=-5\end{cases}\Rightarrow\orbr{\begin{cases}x=-4\\x=-14\end{cases}}}\)
\(\text{q) |x+5|-5=4-(-3)}\)
\(\Rightarrow\left|x+5\right|-5=7\)
\(\Rightarrow\left|x+5\right|=7+5=12\)
\(\Rightarrow\orbr{\begin{cases}x+5=12\\x+5=-12\end{cases}\Rightarrow\orbr{\begin{cases}x=7\\x=-17\end{cases}}}\)
\(\text{h) -|-5|-(-x)+4=3-(-25)}\)
\(\Rightarrow\text{-5+x+4=3+25 }\)
\(\Rightarrow\text{x=3+25+5-4}\)
\(\Rightarrow\text{x=29}\)
Học tốt
@@@Huyền2k7
n) 3-|2x-1|=(-5)
|2x-1|=3-(-5)
|2x-1|=8
\(\hept{\begin{cases}2x-1=8\\2x-1=-8\end{cases}}\)=>\(\hept{\begin{cases}2x=9\\2x=-7\end{cases}}\)=> \(\hept{\begin{cases}x=\frac{9}{2}\\x=\frac{-7}{2}\end{cases}}\)
o) 12+|3-x|=9
|3-x|=9-12
|3-x|=-3
Vì |3-x|\(\ge0\)=> |3-x| không thể bằng -3
=>\(x\in\varnothing\)
p) |x+9|=12+(-9)+2
|x+9|=5
\(\Rightarrow\hept{\begin{cases}x+9=5\\x+9=-5\end{cases}}\Leftrightarrow\hept{\begin{cases}x=-4\\x=-14\end{cases}}\)
q) |x+5|-5=4-(-3)
|x+5|-5=7
=> |x+5|=12\(\Rightarrow\hept{\begin{cases}x+5=12\\x+5=-12\end{cases}}\Leftrightarrow\hept{\begin{cases}x=7\\x=-17\end{cases}}\)
h) -|-5|-(-x)+4=3-(-25)
-5+x+4=3+15
x-1=18
x=19
Chúc bạn học tốt nhé!
Vì \(\left|x-5\right|\ge0\) nên
\(x-5=x+3\)
\(\Leftrightarrow x+x=5-3\)
\(\Leftrightarrow2x=2\)
\(\Leftrightarrow x=\frac{2}{2}=1\)
Vậy \(x=1\)
|x - 5| = x + 3
=> x - 5 = x + 3 hoặc -(x - 5) = x + 3
=> x - x = 3 + 5 hoặc -x + 5 = x + 3
=> 0 = 8, vô lí hoặc 5 - 3 = x + x
=> 2x = 2
=> x = 1
a) x - 7 = - 5
x = - 5 + 7
x = 2
b) 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
c) [ ( 6x - 39 ) : 7 ] . 4 = 12
( 6x - 39 ) : 7 = 12 : 4
( 6x - 39 ) : 7 = 3
6x - 39 = 3 . 7
6x - 39 = 21
6x = 60
x = 10
d) ( x : 3 - 4 ) . 5 = 15
x : 3 - 4 = 3
x : 3 = 7
x = 21
a) x - 7= -5
x= -5 +7
x= 2
b) 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
c)[(6x-39):7].4=12
[(6x-39):7]=12:4
(6x-39):7=3
6x-39=7.3
6x-39=21
6x=21+39
6x=60
x=60:6
x=10
d) ( x :3 -4).5=15
x:3-4=15:5
x:3-4=3
x:3=4+3
x:3=7
x=7.3
x=21
e)(3x -2^4 ).7^3=2. 7^4
(3x-16).343=2.2401
(3x-16).343=4802
3x-16=4802:343
3x-16=14
3x=14+16
3x=30
x=30:3
x=10
g)x-[ 42+(-28)]=-8
x-14=-8
x=-8+14
x=6
i) 4-(7-x)=x -(13-4)
4-7+x=x-13+4
-3 + x= x-9
-3+x=-9+x
=> K có giá trị nào thỏa mãn -3+x=-9+x
=>x thuộc rỗng
= 51/20
----------------------------------
= 3/14
------------------------------------
= 4/7 - 2/7
= 2/7
--------------------------------------
= 17/45
---------------------------------------
= 2/3
--------------------------------------
= 2 x 1/4
= 1/2
a, ( 4,578 x 3 +5,422 x 3 ) : 1,2 -1,2
= [ 3 x ( 4,578 +5,422 ) ] : 1,2 -1,2
= ( 3 x 10 ) : 1,2 -1,2
= 30 : 1,2 -1,2
= 25 -1,2
= 23,8
b, \(\frac{3}{5}\)x\(\frac{9}{7}\)-\(\frac{3}{5}\)x\(\frac{3}{14}\)
= \(\frac{3}{5}\)x ( \(\frac{9}{7}\)- \(\frac{3}{14}\))
= \(\frac{3}{5}\)x\(\frac{15}{14}\)
= \(\frac{9}{14}\)
Chúc bạn học tốt
(4,578 x 3 + 5,422 x 3 ) : 1,2 - 1,2
=( 3 x [4,578 + 5,422 ] : 1,2 - 1,2
=(3 x 10) : 1,2 - 1,2
=30 : 1,2 - 1,2
=25-1.2
=23.8