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A, 70 - 5 . ( x - 3 ) = 45
5.( x - 3 ) = 70 - 45
5. ( x - 3 ) = 25
x - 3 = 25 : 5
x - 3 = 5
x = 5 + 3
x = 8
B, 52x - 3 - 2.52 = 52.3
52x - 3 - 2.25 = 25.3
52x - 3 - 50 = 75
52x - 3 = 75 + 50
52x - 3 = 125
52x - 3 = 53
2x - 3 = 3
2x = 3 + 3
2x = 6
x = 6 : 2
x = 3
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1) -5x - (-3) = 13
\(\Rightarrow-5x+3=13\)
\(\Rightarrow-5x=10\)
\(\Rightarrow x=-2\)
Vậy: \(x=-2\)
2) 15 - ( x - 7) = -21
\(\Rightarrow15-x+7=-21\)
\(\Rightarrow15+7-x=-21\)
\(\Rightarrow22-x=-21\)
\(\Rightarrow x=-22-21=-43\)
Vậy: \(x=-43\)
3) 45 - ( x - 9) = -35
\(\Rightarrow45-x+9=-35\)
\(\Rightarrow45+9-x=-35\)
\(\Rightarrow54-x=-35\)
\(\Rightarrow x=-54-35=-89\)
Vậy: \(x=-89\)
4)/x-2/=3\(\Rightarrow\)ta có 2 t/h:
t/h1: x-2=3\(\Rightarrow\)x=2+3=5
t/h2: x-2=-3\(\Rightarrow\)x=2+(-3)=-1
Vậy x=5 hoặc -1
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\(5\left(7+48:x\right)=45\)
\(\Leftrightarrow\left(7+48x\right)=9\)
\(\Leftrightarrow4x=2\)
\(\Leftrightarrow x=2\)
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\(5^2x-3.2.5^2=5^2.3\)
\(\Leftrightarrow5x^2-3-2.5^2=75\)
\(\Leftrightarrow5x^2-3-50=75\)
\(\Leftrightarrow5x^2-3=125\)
\(\Leftrightarrow5x^2=128\)
\(\Leftrightarrow x^2=\frac{128}{5}\)
\(\Leftrightarrow\orbr{\begin{cases}x=\frac{128}{5}\\x=-\frac{128}{5}\end{cases}}\)
___________________
\(2+x:5=0\)
\(\Leftrightarrow x:5=-2\)
\(\Leftrightarrow x=-10\)
\(10+2x=16\)
\(\Leftrightarrow2x=6\)
\(\Leftrightarrow x=3\)
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\(a,14-5+x=30\)
\(\Rightarrow9+x=30\Rightarrow x=30-9\)
\(\Rightarrow x=21\)
\(b,45-\left(3+x\right)=14\)
\(\Rightarrow3+x=45-14\)
\(\Rightarrow3+x=31\Rightarrow x=31-3\)
\(\Rightarrow x=28\)
\(c,18+\left(-3+x\right)-\left(44-x\right)=55\)
\(\Rightarrow18-3+x-44+x=55\)
\(\Rightarrow2x-29=55\Rightarrow2x=55+29\)
\(\Rightarrow2x=84\Rightarrow x=84:2\)
\(\Rightarrow x=42\)
\(d,\left(x-45\right).27=0\)
\(\Rightarrow x-45=0\Rightarrow x=45\)