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Bài 2: - Xét dấu :
P1 : (-).(+).(-).(-) -> Kết quả cuối cùng là số âm.
P2 : (-).(-).(-).(-).(+) -> Kết quả cuối cùng là số dương.
===> P1 < P2.
Bài 3 :
a) \(x\cdot\left(x-1\right)=0\)
\(\Rightarrow\left[\begin{matrix}x=0\\x-1=0\end{matrix}\right.\rightarrow\left[\begin{matrix}x=0\\x=1\end{matrix}\right.\)
b) \(\left(x-3\right)\cdot\left(x+4\right)=0\)
\(\left[\begin{matrix}x-3=0\\x+4=0\end{matrix}\right.\rightarrow\left[\begin{matrix}x=3\\x=-4\end{matrix}\right.\)
c) \(\left(2x-4\right)\cdot\left(x+2\right)=0\rightarrow\left[\begin{matrix}2x-4=0\\x+2=0\end{matrix}\right.\rightarrow\left[\begin{matrix}x=2\\x=-2\end{matrix}\right.\)
d) \(\left(x+1\right)^2\cdot\left(x-2\right)^2=0\rightarrow\left[\begin{matrix}x+1=0\\x-2=0\end{matrix}\right.\rightarrow\left[\begin{matrix}x=-1\\x=2\end{matrix}\right.\)
e) \(x\cdot\left(x+1\right)\cdot\left(x+2\right)^2\cdot\left(x+3\right)^3=0\)
\(\Rightarrow\left[\begin{matrix}x=0\\x+1=0\\x+2=0\\x+3=0\end{matrix}\right.\rightarrow\left[\begin{matrix}x=0\\x=-1\\x=-2\\x=-3\end{matrix}\right.\)
f) \(\left(x-9^5\right)\cdot\left(x-5\right)^8=0\)
\(\Rightarrow\left[\begin{matrix}x-9=0\\x-5=0\end{matrix}\right.\rightarrow\left[\begin{matrix}x=9\\x=5\end{matrix}\right.\)
g) \(x\cdot\left(x+100\right)^{10}\cdot\left(x+2000\right)^{20}\cdot\left(x+300\right)^{3000}=0\)
\(\Rightarrow\left[\begin{matrix}x=0\\x+100=0\\x+2000=0\\x+300=0\end{matrix}\right.\rightarrow\left[\begin{matrix}x=0\\x=-100\\x=-2000\\x=-300\end{matrix}\right.\)
h) \(\left(x-2\right)^2=0\rightarrow x=2\)
Bài 1:tìm x thuộc Z
a)x.(x-1)=0
\(\Leftrightarrow\left[\begin{matrix}x=0\\x-1=0\end{matrix}\right.\Leftrightarrow\left[\begin{matrix}x=0\\x=1\end{matrix}\right.\)
Vậy: \(x=0;1\)
b)(x-3).(x+4)=0
\(\Leftrightarrow\left[\begin{matrix}x-3=0\\x+4=0\end{matrix}\right.\Leftrightarrow\left[\begin{matrix}x=3\\x=-4\end{matrix}\right.\)
Vậy: \(x=3;-4\)
c)(2x-4).(x+2)=0
\(\Leftrightarrow2\left(x-2\right).\left(x+2\right)=0\)
\(\Leftrightarrow\left[\begin{matrix}x-2=0\\x+2=0\end{matrix}\right.\Leftrightarrow\left[\begin{matrix}x=2\\x=-2\end{matrix}\right.\)
Vậy: \(x=2;-2\)
d)(x+1)^2.(x-2)^2=0
\(\Leftrightarrow\left[\begin{matrix}x+1=0\\x-2=0\end{matrix}\right.\Leftrightarrow\left[\begin{matrix}x=-1\\x=2\end{matrix}\right.\)
Vậy: \(x=-1;2\)
e) x(x+1).(x+2)^2.(x+3)^3=0
\(\Leftrightarrow\left[\begin{matrix}x=0\\x+1=0\\x+2=0\\x+3=0\end{matrix}\right.\Leftrightarrow\left[\begin{matrix}x=0\\x=-1\\x=-2\\x=-3\end{matrix}\right.\)
Vậy: \(x=0;-1;-2;-3\)
f)(x-9)^5.(x-5)^8=0
\(\Leftrightarrow\left[\begin{matrix}x-9=0\\x-5=0\end{matrix}\right.\Leftrightarrow\left[\begin{matrix}x=9\\x=5\end{matrix}\right.\)
Vậy: \(x=9;5\)
g)x(x+100)^10.(x+2000)^20.(x+300)^300=0
\(\Leftrightarrow\left[\begin{matrix}x=0\\x+100=0\\x+200=0\\x+300=0\end{matrix}\right.\Leftrightarrow\left[\begin{matrix}x=0\\x=-100\\x=-200\\x=-300\end{matrix}\right.\)
Vậy: \(x=0;-100;-200;-300\)
h)(x-2)^2=0
\(\Leftrightarrow x-2=0\)
\(\Leftrightarrow x=2\)
Vậy: \(x=2\)
Bài 1:
a, \(x^2\) +2\(x\) = 0
\(x.\left(x+2\right)\) = 0
\(\left[{}\begin{matrix}x=0\\x+2=0\end{matrix}\right.\)
\(\left[{}\begin{matrix}x=0\\x=-2\end{matrix}\right.\)
\(x\) \(\in\) {-2; 0}
b, (-2.\(x\)).(-4\(x\)) + 28 = 100
8\(x^2\) + 28 = 100
8\(x^2\) = 100 - 28
8\(x^2\) = 72
\(x^2\) = 72 : 8
\(x^2\) = 9
\(x^2\) = 32
|\(x\)| = 3
\(\left[{}\begin{matrix}x=-3\\x=3\end{matrix}\right.\)
Vậy \(\in\) {-3; 3}
c, 5.\(x\) (-\(x^2\)) + 1 = 6
- 5.\(x^3\) + 1 = 6
5\(x^3\) = 1 - 6
5\(x^3\) = - 5
\(x^3\) = -1
\(x\) = - 1
1 a= 300.3=900
b= 204.(-8).5
= (-1632).5=(-8160)
2
A= 365.72.(-11).(-10)
B= (-714).(-232).(-72)
A= 26280.110
B= 165648.(-72)
A= 2890800
B= (-11926656) A lớn hơn B
3 a 2x-5=15
2x= 15+5
2x= 20
x = 20:2
x=10
\(a,-12\left(x-5\right)+7\left(3-x\right)=5\)
\(-12x+60+21-7x=5\)
\(-12x-7x=5-60-21\)
\(-19x=-76\Leftrightarrow x=4\)
\(b,30\left(x+2\right)-6\left(x-5\right)-24x=100\)
\(30x+60-6x+30-24x=100\)
\(30x-6x-24x=100-60-30\)
\(0x=10\left(vl\right)\)
Vậy pt vô nghiệm
A , 3 - ( 17 - x ) = 289 - ( 36 + 289 )
3 - 17 + x = 0 - 36
-14 + x = -36
x = -36 - ( - 14 ) = -22
B, 25 - ( x + 5 ) = -415 - ( 15 - 415 )
25 - x - 5 = 0 - 15
20 - x = -15
x = 20 - ( - 15 ) = 35
C , 34 + ( 21 - x ) = ( 3747 - 30 ) - 3746
34 + 21 - x = 1 - 30
55 - x = -29
x = 55 - (-29 ) = 74
D , -2x - ( x -17 ) = 34 - ( -x + 25 )
- 2x - x + 17 = 34 - 25 + x
- 3x + 17 = 9 + x
- 3x - x = 9 - 17
-4x = -8
x = -8 : ( - 4 )
x = 2
E , 17x + ( -16x - 37 ) = x + 43
17x - 16x -37 = x + 43
x - 37 = x + 43
-37 - 43 = x - x
- 80 = 0 ( vô lý )
G , ( x + 12 ) . (x - 3 ) = 0
\(\hept{\begin{cases}x+12=0\\x-3=0\end{cases}}\)
\(\hept{\begin{cases}x=-12\\x=3\end{cases}}\)
1) x - 2 = -6
x = -6 + 2
x = -4
2) -5 . x - ( -3 ) =13
-5 . x = 13 + ( -3 )
-5 . x = 10
x = 10 : ( -5 )
x = -2
Bài 3:
a: x(x-1)=0
=>x=0 hoặc x-1=0
=>x=0 hoặc x=1
b: (x-3)(x+4)=0
=>x-3=0 hoặc x+4=0
=>x=3 hoặc x=-4
c: (2x-4)(x+2)=0
=>2x-4=0 hoặc x+2=0
=>x=2 hoặc x=-2
d: (x+1)2(x-2)2=0
=>x+1=0 hoặc x-2=0
=>x=-1 hoặc x=2