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\(a,x=\dfrac{210}{-35}=-6\\ b,x=\dfrac{42}{-7}=-6\\ c,x=\dfrac{180}{-12}=-15\\ d,x=3-5=-2\)
Bài 2:
a: 2/5=14/35
3/7=15/35
b: -3/4=-9/12
-7/-12=7/12
c: 5/9=60/108
-11/-12=11/12=99/108
d: -4/7=-36/63
8/9=56/63
-10/21=-30/63
Bài 2:
a: 2/5=14/35
3/7=15/35
b: -3/4=-9/12
-7/-12=7/12
c: 5/9=60/108
-11/-12=11/12=99/108
d: -4/7=-36/63
8/9=56/63
-10/21=-30/63
c: 90\(⋮\)x-2
=>\(x-2\in\){1;-1;2;-2;3;-3;5;-5;6;-6;9;-9;10;-10;15;-15;18;-18;30;-30;45;-45;90;-90}
=>x\(\in\){3;1;4;0;5;-1;7;-3;8;-4;11;-7;12;-8;17;-13;20;-16;32;-28;47;-43;92;-88}
mà 10<=x<=90
nên \(x\in\left\{11;12;17;20;32;47\right\}\)
d: \(x⋮12\)
=>\(x\in\left\{0;12;24;36;48;60;72;...\right\}\)
mà 30<=x<=60
nên \(x\in\left\{36;48;60\right\}\)
a: x-140:35=270
=>x-4=270
=>x=270+4=274
b: \(\left(3x-1\right)^2-3^2=4^2\)
=>(3x-1)2-9=16
=>\(\left(3x-1\right)^2=25\)
=>\(\left[{}\begin{matrix}3x-1=5\\3x-1=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}3x=6\\3x=-4\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}x=2\\x=-\dfrac{4}{3}\end{matrix}\right.\)
a) \(\dfrac{x}{-6}=\dfrac{-15}{45}\)
\(\dfrac{-x}{6}=\dfrac{-15}{45}\)
\(\dfrac{x}{6}=\dfrac{15}{45}\)
\(x=\dfrac{\left(15\cdot6\right)}{45}\)
\(x=2\)
b) \(\dfrac{x}{5}=\dfrac{16}{25}\)
\(x=\dfrac{\left(16\cdot5\right)}{25}\)
\(x=\dfrac{80}{25}\)
\(x=\dfrac{16}{5}\)
c) \(\dfrac{5}{x-3}=\dfrac{20}{-12}\)
\(x-3=\dfrac{\left(5\cdot-12\right)}{20}\)
\(x-3=-3\)
\(x=\left(-3\right)+3\)
\(x=0\)
d) \(\dfrac{2}{5}\cdot x=\dfrac{6}{35}\)
\(x=\dfrac{6}{35}\div\dfrac{2}{5}\)
\(x=\dfrac{3}{7}\)
\(a,\dfrac{x}{7}=\dfrac{6}{21}\Rightarrow x.21=7.6=42\\ \Rightarrow x=2\\ b,\dfrac{1}{2}=\dfrac{x}{12}\Rightarrow1.12=2.x=12\\ \Rightarrow x=6\\ c,\dfrac{-7}{6}=\dfrac{x}{12}\Rightarrow-7.12=6.x=-84\\ \Rightarrow x=-14\)
a) \(\dfrac{1}{7}< \dfrac{x}{35}< \dfrac{2}{5}\)
\(\Rightarrow\dfrac{5}{35}< \dfrac{x}{35}< \dfrac{14}{35}\)
\(\Rightarrow5< x< 14\)
b) \(\dfrac{5}{13}< 2-x< \dfrac{5}{8}\)
\(\Rightarrow2-\dfrac{5}{8}< x< 2-\dfrac{5}{13}\)
\(\Rightarrow\dfrac{11}{8}< x< \dfrac{21}{13}\)
a: -26-(x-7)=0
=>x-7=-26
=>x=-26+7=-19
b: \(24-\left(30+x\right)=-7\)
=>\(30+x=24-\left(-7\right)\)
=>\(x+30=24+7=31\)
=>x=31-30=1
c: \(3-\left(17-x\right)=-12\)
=>\(17-x=3-\left(-12\right)\)
=>\(17-x=3+12=15\)
=>x=17-15=2
d: \(\left(5-x\right)-7=-15\)
=>\(5-x=-15+7=-8\)
=>\(x=5-\left(-8\right)=5+8=13\)
a,xy=2
=>x=2 ; y =1 hoặc x=1 ;y=2
b,xy=6
=>x=2;y=3 hoặc x=3 ; y=3
c,xy=12
=>x=2;y=6 hoặc x=6;y=2
=>x=3;y=4 hoặc x=4;y=3
d,xy=40 (x>y)
vì x>y
=>x=8;y=5
e,xy=30 (x<y)
vì x<y
x=5;y=6
a, x = \(\dfrac{-210}{-35}=6\)
b, x = \(\dfrac{42}{-7}=-6\)
c, x = \(\dfrac{180}{-12}=-15\)
d, x2 = 9
=> x = 3 hoặc x = -3
(-35).x=-210
x =210:35
x =6