42 + (-19) + 158+ (-18) + 1
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( x-2) .3 =18 135-3(x+1)=30
(x-2) =18:3 3(x+1)=135-30
(x-2) =6 3(x+1)=105
x =6+2 x+1 =105:3
x =8 x+1 =35
x =35-1
x =34
(123-x)-72=28 (158-x):7=28
(123-x) =28+72 (158-x) =28.7
(123-x) =100 (158-x) =784
x =123-100 x =158-784
x =23 x =-626
42.x=39.42-37.42
42.x=42.(39-37)
42.x=42.2
x=42.2:42
x =2
bài này dài lắm đó k mik nha
a) \(\dfrac{25}{37}\times\dfrac{18}{29}+\dfrac{18}{29}\times\dfrac{12}{37}\)
\(=\dfrac{18}{29}\times\left(\dfrac{25}{37}+\dfrac{12}{37}\right)\)
\(=\dfrac{18}{29}\times\dfrac{37}{37}\)
\(=\dfrac{18}{29}\times1\)
\(=\dfrac{18}{29}\)
b) \(\dfrac{31}{85}\times\dfrac{11}{19}+\dfrac{31}{85}\times\dfrac{12}{19}-\dfrac{42}{19}\times\dfrac{31}{85}\)
\(=\dfrac{31}{85}\times\left(\dfrac{11}{19}+\dfrac{12}{19}-\dfrac{42}{19}\right)\)
\(=\dfrac{31}{85}\times\dfrac{-19}{19}\)
\(=\dfrac{31}{85}\times-1\)
\(=-\dfrac{31}{85}\)
c) \(\dfrac{16}{53}:\dfrac{17}{9}-\dfrac{16}{53}:\dfrac{17}{8}\)
\(=\dfrac{16}{53}:\left(\dfrac{9}{17}-\dfrac{8}{17}\right)\)
\(=\dfrac{16}{53}:\dfrac{1}{17}\)
\(=\dfrac{16}{901}\)
c) \(\dfrac{1}{5}\times\dfrac{12}{31}\times\dfrac{4}{3}+\dfrac{19}{31}\times\dfrac{4}{15}\)
\(=\dfrac{4}{15}\times\dfrac{12}{31}+\dfrac{19}{31}\times\dfrac{4}{15}\)
\(=\dfrac{4}{15}\times\left(\dfrac{12}{31}+\dfrac{19}{31}\right)\)
\(=\dfrac{4}{15}\times\dfrac{31}{31}\)
\(=\dfrac{4}{15}\times1\)
\(=\dfrac{4}{15}\)
a: =18/29*(25/37+12/37)
=18/29
b: =31/85(11/19+12/19-42/19)
=-31/85
c; =16/53(9/17+8/17)=16/53
d: =4/15(12/31+19/31)=4/15
x - 18 - 42 = 23 - 43 - 70 - x
\(\rightarrow\) 2x = -30
\(\rightarrow\) x = -15
\(\left(-\left(x+15\right)\right)^2\) - 19 = \(3^2\) .5
\(\rightarrow\)\(x^2+30x+225\) - 19 = 45
\(\rightarrow x^2+30x+161=0\)
\(\rightarrow x^2+23x+7x+161=0\)
\(\rightarrow x\left(x+23\right)+7\left(x+23\right)=0\)
\(\rightarrow\left(x+7\right)\left(x+23\right)=0\)
\(\rightarrow\) x = -7 hoặc x = -23
\(=\left(\dfrac{19}{42}+\dfrac{23}{42}\right)+\left(\dfrac{1}{37}+\dfrac{36}{37}\right)+10\)
=12