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a/(-100)-12=-100+(-12)=-112
b/x=-18-(-15)=-18+15=-3
c/-14+x=10-(-15)=10+15=25
x=-14-25
x=-39
d.x-(-19)=0+(-11)=-11
x+19=-11
x=-11-19
x=-30
a) \(12+x+\left(-5\right)=-18-2x\)
\(\Rightarrow12+x-5=-18-2x\)
\(\Rightarrow x+7+18+2x=0\)
\(\Rightarrow3x=-25\)
\(\Rightarrow x=-\dfrac{25}{3}\)
b) \(\left(-14\right)-x+\left(-15\right)=-10+\left(4-2x\right)\)
\(\Rightarrow-14-x-15=-10+4-2x\)
\(\Rightarrow-x-29=-2x-6\)
\(\Rightarrow-x+2x=-6+29\)
\(\Rightarrow x=23\)
c) \(x-\left(-19\right)-\left(-11\right)=-\left(3x+40\right)\)
\(\Rightarrow x+19+11=-3x-40\)
\(\Rightarrow x+30=-3x-40\)
\(\Rightarrow x+3x=-40-30\)
\(\Rightarrow4x=-70\)
\(\Rightarrow x=-\dfrac{35}{2}\)
14) (x - 2) . (x + 4) = 0
\(\Rightarrow\) x - 2 = 0 hoặc x + 4 = 0
Nếu x - 2 = 0
x = 0 + 2
x = 2
Nếu x + 4 = 0
x = 0 - 4
x = -4
Vậy x \(\in\) {2 ; -4)
15) (x - 2) . (x + 15) = 0
\(\Rightarrow\) x - 2 = 0 hoặc x + 15 = 0
Nếu x - 2 = 0
x = 0 + 2
x = 2
Nếu x + 15 = 0
x = 0 - 15
x = -15
Vậy x \(\in\) {-15 ; 2}
1)4+x=7
=>x=7-4=3
2)2x+(-5)=-18
=>2x=-18-(-5)=-18+5=-13
=>x=-13:2=-13/2
=>x thuộc rỗng
(-14)+x-7=10
=>(-14)+x=10+7=17
a) Ta có: \(\dfrac{x-2}{15}+\dfrac{x-3}{14}+\dfrac{x-4}{13}+\dfrac{x-5}{12}=4\)
\(\Leftrightarrow\dfrac{x-2}{15}-1+\dfrac{x-3}{14}-1+\dfrac{x-4}{13}-1+\dfrac{x-5}{12}-1=0\)
\(\Leftrightarrow\dfrac{x-17}{15}+\dfrac{x-17}{14}+\dfrac{x-17}{13}+\dfrac{x-17}{12}=0\)
\(\Leftrightarrow\left(x-17\right)\left(\dfrac{1}{15}+\dfrac{1}{14}+\dfrac{1}{13}+\dfrac{1}{12}\right)=0\)
mà \(\dfrac{1}{15}+\dfrac{1}{14}+\dfrac{1}{13}+\dfrac{1}{12}>0\)
nên x-17=0
hay x=17
Vậy: x=17
b) Ta có: \(\dfrac{x+1}{19}+\dfrac{x+2}{18}+\dfrac{x+3}{17}+...+\dfrac{x+18}{2}+18=0\)
\(\Leftrightarrow\dfrac{x+1}{19}+1+\dfrac{x+2}{18}+1+\dfrac{x+3}{17}+1+...+\dfrac{x+18}{2}+1=0\)
\(\Leftrightarrow\dfrac{x+20}{19}+\dfrac{x+20}{18}+\dfrac{x+20}{17}+...+\dfrac{x+20}{2}=0\)
\(\Leftrightarrow\left(x+20\right)\left(\dfrac{1}{19}+\dfrac{1}{18}+\dfrac{1}{17}+...+\dfrac{1}{2}\right)=0\)
mà \(\dfrac{1}{19}+\dfrac{1}{18}+\dfrac{1}{17}+...+\dfrac{1}{2}>0\)
nên x+20=0
hay x=-20
Vậy: x=-20
4+x=7
x+(-15)=-18
(-14)+x-7=-10
(-12)-x-(-19)=0