20|3-(-7)|+2X=3X-1
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a. 5x.(12x+7)-3x.(20x-5)=-150
x=-3
b. ( 2x-1).(3-x)+(x+4).(2x-5)=20
x=43/10
c. 9x2-1+(3x-1)2=0
x=1/3
d. 3x.(x-2)-(3x+2).(x-1)=7
x=-5/2
e. (2x-1)2-(2x+5).(2x-5)=20
x=3/2
f. 4x2-5=4
x=3/2
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\(1) 2x+1=15-5x \)
\(⇔2x+5x=15-1\)
\(⇔7x=14\)
\(⇔x=2\)
vậy pt có 1 nghiệm là x=2
\(2) 3x-2=2x+5\)
\(⇔3x-2x=5+2\)
\(⇔x=7\)
vậy pt có 1 nghiệm là x=7
\(3) 7(x-2)=5(3x+1)\)
\(⇔7x-14=15x+5\)
\(⇔7x-15x=5+14\)
\(⇔-8x=19\)
\(⇔x=-\dfrac{19}{8}\)
vậy pt có 1 nghiệm là x=-\(\dfrac{19}{8}\)
\(4) 2x+5=20-3x\)
\(⇔2x+3x=20-5\)
\(⇔5x=15\)
\(⇔x=3\)
vậy pt có 1 nghiệm là x=3
\(5) -4x+8=0\)
\(⇔-4x=-8\)
\(⇔x=2\)
vậy pt có 1 nghiệm là x=2
\(6) x-3=10-5x\)
\(⇔x+5x=10+3\)
\(⇔6x=13\)
\(⇔x=\dfrac{13}{6}\)
vậy pt có 1 nghiệm là \(x=\dfrac{13}{6}\)
\(7) 3x-1=x+3\)
\(⇔3x-x=3+1\)
\(⇔2x=4\)
\(⇔x=2\)
vậy pt có 1 nghiệm là x=2
\(8) 2(x+1)=5x-7\)
\(⇔2x+2=5x-7\)
\(⇔2x-5x=-7-2\)
\(⇔-3x=-9\)
\(⇔x=3\)
vậy pt có 1 nghiệm là x=3.
![](https://rs.olm.vn/images/avt/0.png?1311)
1/2x^3y(2x^4y^3-4xy-6)
=1/2x^3y*2x^4y^3-1/2x^3y*4xy-1/2x^3y*6
=x^7y^4-2x^4y^2-3x^3y
![](https://rs.olm.vn/images/avt/0.png?1311)
Tìm x:
1. 3x (2x + 3) - (2x + 5).(3x - 2) = 8
\(\Leftrightarrow6x^2+9x-6x^2+4x-15x+10=0 \)
\(\Leftrightarrow-2x+10=0\Leftrightarrow x=5\)
Vậy x = 5
2. 4x (x -1) - 3(x2 - 5) -x2 = (x - 3) - (x + 4)
\(\Leftrightarrow4x^2-4x-3x^2+15-x^2=x-3-x-4\)
\(\Leftrightarrow-4x+15=-7\)
\(\Leftrightarrow-4x=-22\Leftrightarrow x=\frac{11}{2}\)
Vậy x = \(\frac{11}{2}\)
3. 2 (3x -1) (2x +5) - 6 (2x - 1) (x + 2) = -6
\(\Leftrightarrow2\left(6x^2+15x-2x-5\right)-6\left(2x^2+4x-x-2\right)=-6\)
\(\Leftrightarrow12x^2+30x-4x-10-12x^2-24x+6x+12=-6\)
\(\Leftrightarrow8x=-8\Leftrightarrow x=-1\)
Vậy x = -1
4. 3 ( 2x - 1) (3x - 1) - (2x - 3) (9x - 1) - 3 = -3
\(\Leftrightarrow3\left(6x^2-2x-3x+1\right)-18x^2+2x+27x-3-3=-3\)
\(\Leftrightarrow18x^2-6x-9x+3-18x^2+2x+27x-6=-3\)
\(\Leftrightarrow14x=0\Leftrightarrow x=0\)
Vậy x = 0
5. (3x - 1) (2x + 7) - ( x + 1) (6x - 5) = (x + 2) - (x - 5)
\(\Leftrightarrow6x^2+21x-2x-7-6x^2+5x-6x+5=7\)
\(\Leftrightarrow18x=9\Leftrightarrow x=\frac{1}{2}\)
Vậy x = \(\frac{1}{2}\)
6. 3xy (x + y) - (x + y) (x2 + y2 + 2xy) + y3 = 27
\(\Leftrightarrow3x^2y+3xy^2-\left(x+y\right)^3+y^3=27\)
\(\Leftrightarrow3x^2y+3xy^2-x^3-y^3-3x^2y-3xy^2+y^3=27\)
\(\Leftrightarrow-x^3=27\)
\(\Leftrightarrow x=-3\)
Vậy x = -3
7. 3x (8x - 4) - 6x (4x - 3) = 30
\(\Leftrightarrow24x^2-12x-24x^2+12x=30\)
\(\Leftrightarrow0=30\) ( vô lý)
Vậy pt vô nghiệm
8. 3x (5 - 2x) + 2x (3x - 5) = 20
\(\Leftrightarrow15x-6x^2+6x^2-10x=20\)
\(\Leftrightarrow5x=20\Leftrightarrow x=4\)
Vậy x = 4
![](https://rs.olm.vn/images/avt/0.png?1311)
20) -5-(x + 3) = 2 - 5x ⇔ -5 - x - 3 = 2 -5x ⇔ 4x = 10 ⇔ x = \(\frac{5}{2}\)
Vậy...
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a) Ta có: \(3x\left(x+1\right)-2x\left(x+20\right)=-1-x\)
\(\Leftrightarrow3x^2+3x-2x^2-40x+1+x=0\)
\(\Leftrightarrow x^2-36x+1=0\)
\(\Leftrightarrow x^2-36x+324-323=0\)
\(\Leftrightarrow\left(x-18\right)^2=323\)
\(\Leftrightarrow\left[{}\begin{matrix}x-18=\sqrt{323}\\x-18=-\sqrt{323}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=18+\sqrt{323}\\x=18-\sqrt{323}\end{matrix}\right.\)
Vậy: \(x\in\left\{18+\sqrt{323};18-\sqrt{323}\right\}\)
b) Ta có: \(\left(3x-1\right)\left(2x+7\right)-\left(x+1\right)\left(6x-5\right)=16\)
\(\Leftrightarrow6x^2+21x-2x-7-\left(6x^2-5x+6x-5\right)-16=0\)
\(\Leftrightarrow6x^2+19x-7-\left(6x^2+x-5\right)-16=0\)
\(\Leftrightarrow6x^2+19x-7-6x^2-x+5-16=0\)
\(\Leftrightarrow18x-18=0\)
\(\Leftrightarrow18x=18\)
hay x=1
Vậy: x=1
c) Ta có: \(\left(10x+9\right)\cdot x-\left(5x-1\right)\left(2x+3\right)=8\)
\(\Leftrightarrow10x^2+9x-\left(10x^2+15x-2x-3\right)-8=0\)
\(\Leftrightarrow10x^2+9x-10x^2-13x+3-8=0\)
\(\Leftrightarrow-4x-5=0\)
\(\Leftrightarrow-4x=5\)
hay \(x=\frac{-5}{4}\)
Vậy: \(x=\frac{-5}{4}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
x + 12 =(-5)-x
x + x = -5 - 12
2x = -17
\(x=-\frac{17}{2}\)
x + 5 = 10 - x
x + x = 10 - 5
2x = 5
\(x=\frac{5}{2}\)
12-x=x+1
12 - 1 = x+x
11=2x
x=\(\frac{11}{2}\)
14+4x=3x-20
4x-3x=-20-14
x=-34
20|3-(-7)|+2x=3x-1
20|10|+2x=3x-1
20.10+2x=3x-1
200+2x=3x-1
-x=-201
x=201
#H