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a) Ta có: \(\left(x-3\right)\left(x-5\right)< 0\)
\(\Rightarrow\hept{\begin{cases}x-3< 0\\x-5>0\end{cases}}\)hoặc \(\hept{\begin{cases}x-3>0\\x-5< 0\end{cases}}\)
\(\Rightarrow\hept{\begin{cases}x< 3\\x>5\end{cases}}\) (vô lý) hoặc \(\hept{\begin{cases}x>3\\x< 5\end{cases}}\)(thỏa mãn).
Vậy 3 < x < 5 thì (x-3)(x-5) <0.
b) \(-6x-\left(-7\right)=25\)
\(\Rightarrow-6x=25-7\)
\(\Rightarrow-6x=18\Rightarrow x=\frac{18}{-6}=-3\)
Vậy x = -3.
c) \(46-\left(x-11\right)=-48\)
\(\Rightarrow46-x+11=-48\)
\(\Rightarrow46+11+48=x\Rightarrow x=105\).
d) \(\left(x+15\right)\left(x-2\right)=0\)
\(\Rightarrow\)x + 15 = 0 hoặc x - 2 = 0
\(\Rightarrow x=-15\)hoặc \(x=2\).
e) \(3\left(4-x\right)-2\left(x-5\right)=12\)
\(\Rightarrow12-3x-2x+10=12\)
\(\Rightarrow-3x-2x=12-10-12\)
\(\Rightarrow-5x=-10\Rightarrow x=2\).
Chúc bn hc tốt!
a) (-12)2.x = 56 + 10.13x
=> 144.x = 56 + 130x
=> 144x - 130x = 56
=> 14x = 56
=>x = 56 : 14
=> x = 4
b) 80 - (x2 + 5) = 66
=> x2 + 5 = 80 - 66
=> x2 + 5 = 14
=> x2 = 14 - 5
=> x2 = 9
=> x2 = 32
=> \(\orbr{\begin{cases}x=3\\x=-3\end{cases}}\)
c) 9 - 25 = (7 - x) - (25 + 7)
=> -16 = (7 - x) - 32
=> 7 - x = -16 + 32
=> 7 - x = 16
=> x = 7 - 16
=> x = -9
d) \(\left(x+5\right)^2=16\)
=> \(\left(x+5\right)^2=4^2\)
=> \(\orbr{\begin{cases}x+5=4\\x+5=-4\end{cases}}\)
=> \(\orbr{\begin{cases}x=-1\\x=-9\end{cases}}\)
a) \(M=\left(71+x\right)-\left(-24-x\right)+\left(-35-x\right)\)
\(=71+x-\left(-24\right)+x+\left(-35\right)-x\)
\(=60+x\)
b) \(x-34-\left[\left(15+x\right)-\left(23-x\right)\right]\)
\(=x-34-\left(15+x-23+x\right)\)
\(=x-34-\left(-8+2x\right)\)
\(=x-34-\left(-8\right)-2x\)
\(=-26-x\)
c) \(\left(-15+\left|x\right|\right)+\left(25-\left|x\right|\right)\)
\(=-15+\left|x\right|+25-\left|x\right|\)
\(=10\)
10 - { [ ( x : 3 + 17 ) : 10 + 3 : 24 ] : 10 } = 5
[ ( x : 3 + 17 ) : 10 + 3 : 24 ] : 10 = 10 - 5 = 5
( x : 3 + 17 ) : 10 + 3 : 24 = 5 x 10
( x : 3 + 17 ) : 10 + 48 = 50
( x : 3 + 17 ) : 10 = 50 - 48
( x : 3 + 17 ) : 10 = 2
x : 3 + 17 = 2 x 10
x : 3 + 17 = 20
x : 3 = 20 - 17 = 3
x = 3 x 3 = 9
a) [(2x+14) : 4 - 3] : 2 = 1
(2x+14) : 4 - 3 = 1/2
(2x+14) : 4 = 1/2 + 3
(2x+14) : 4 = 7/2
2x+14 = 7/2 . 1/4
2x = 7/8 - 1/4
2x = 5/8
x= 5/8.1/2
x= 5/16
\(1\)) \(70:\frac{4x+720}{x}=\frac{1}{2}\)
\(\Leftrightarrow\frac{4x+720}{x}=70:\frac{1}{2}\)
\(\Leftrightarrow\frac{4x+720}{x}=140\)
\(\Leftrightarrow\left(4x+720\right):x=140\)
\(\Leftrightarrow4x+720=140.x\)
\(\Leftrightarrow4x-140x=-720\)
\(\Leftrightarrow x.\left(-136\right)=-720\)
\(\Leftrightarrow x=-720:\left(-136\right)\)
\(\Leftrightarrow x=\frac{90}{17}\)
\(2\)) Mình đang nghĩ
b ) 2. | x | - 15= -7
2. | x | = -7 + 15
2. | x | = 8
| x | = 8 : 2
| x | = 4
⇒ x = 4 , x = -4
Vậy x = 4 hoặc - 4
c) ( - 187 ) + 1948- ( -287 ) + | -1948 | + | - 1918 |
= ( - 187 ) + 1948- ( -287 ) + 1948 + 1918
= 1761- 1211+ 3866
= 550 + 3866
= 4416
=4