1/ \(7x-5=13-5x\)

\(\Leftrightarrow12x=18\)

\(\Leftrightarrow x=\dfrac{3}{2}\)

Vậy: \(S=\left\{\dfrac{3}{2}\right\}\)

==========

2/ \(19+3x=5-18x\)

\(\Leftrightarrow21x=-14\)

\(\Leftrightarrow x=-\dfrac{2}{3}\)

Vậy: \(S=\left\{-\dfrac{2}{3}\right\}\)

==========

3/ \(x^2+2x-4=-12+3x+x^2\)

\(\Leftrightarrow-x=-8\)

\(\Leftrightarrow x=8\)

Vậy: \(S=\left\{8\right\}\)

===========

4/ \(-\left(x+5\right)=3\left(x-5\right)\)

\(\Leftrightarrow-x-5=3x-15\)

\(\Leftrightarrow-4x=-10\)

\(\Leftrightarrow x=\dfrac{5}{2}\)

Vậy: \(S=\left\{\dfrac{5}{2}\right\}\)

==========

5/ \(3\left(x+4\right)=\left(-x+4\right)\)

\(\Leftrightarrow3x+12=-x+4\)

\(\Leftrightarrow4x=-8\)

\(\Leftrightarrow x=-2\)

Vậy: \(S=\left\{-2\right\}\)

[----------]

1. \(7x-5=13-5x\) \(\Leftrightarrow12x=18\Leftrightarrow x=\dfrac{3}{2}\)

2. \(19+3x=5-18x\Leftrightarrow21x=-14\Leftrightarrow x=-\dfrac{2}{3}\)

3. \(x^2+2x-4=-12+3x+x^2\Leftrightarrow-x=-8\Leftrightarrow x=8\)

4. \(-\left(x+5\right)=3\left(x-5\right)\Leftrightarrow-x-5=3x-15\Leftrightarrow4x=10\Leftrightarrow x=\dfrac{5}{2}\)

5. \(3\left(x+4\right)=-x+4\Leftrightarrow3x+12=-x+4\Leftrightarrow4x=-8\Leftrightarrow x=-2\)

1) Ta có: \(7x-5=13-5x\)

\(\Leftrightarrow12x=18\)

hay \(x=\dfrac{3}{2}\)

2) Ta có: \(19+3x=5-18x\)

\(\Leftrightarrow21x=-14\)

hay \(x=-\dfrac{2}{3}\)

3) Ta có: \(x^2+2x-4=x^2+3x-12\)

\(\Leftrightarrow3x-12=2x-4\)

hay x=8

4) Ta có: \(-\left(x+5\right)=3\left(x-5\right)\)

\(\Leftrightarrow-x-5-3x+15=0\)

\(\Leftrightarrow-4x=-10\)

hay \(x=\dfrac{5}{2}\)

4(x−5)−(3x−1)=x−19

⇒4x−20−3x+1=x−19

⇒4x−3x−x=−19+20−1

⇒0x=0

⇒x∈R

Chúc bạn học tốt nhé! ^^

\(\text{4(x-5)-(3x-1)=x-19}\)

\(4x-20-3x+1=x-19\)

\(4x-3x-x=-19-1+20\)

\(0=0??\)

\(4\left(x-5\right)-\left(3x-1\right)=x-19\)

\(\Leftrightarrow4x-20-3x+1=x-1\)

\(\Leftrightarrow-19=-1\) ( vô lí )

Vậy pt vô nghiệm

a) = 17/19 - 17/19 + 27/35 + 35/35 = 0 + 62/35

b) = 1/3 x 4/5 + 1/3 x6/5 + 1/3 x 2 = 1/3(4/5 + 6/5 + 2) = 1/3 x 4 = = 4/3

c) 4/7 x 2/9 + 4/7 x 7/9 + 2/3 = 4/7 x (2/9 + 7/9) + 2/3 = 4/7 x 1 + 2/3 = 26/21

A) 17/19 - 17/19 + 27/35 + 35/35 = 0 + 62/35

B) 1/3 x 4/5 + 1/3 x 6/5 + 1/3 x 2 = 1/3 x(4/5 + 6/5 x 2 ) = 1/3 x 4 = 4/3

c) TƯƠNG TỰ CÂU A VÀ B

* HOKTOT*

NHA

A,

a: \(\Leftrightarrow x^2-4-4x^2-4x-1-2x+3x^2=0\)

=>-6x-5=0

=>-6x=5

hay x=-5/6

b: \(\Leftrightarrow2x^3+8x^2+8x-8x^2-2x^3+16=0\)

=>8x+16=0

hay x=-2

c: \(\Leftrightarrow x^3-6x^2+12x-8+9x^2-1-x^3-3x^2-3x-1=0\)

=>9x-10=0

hay x=10/9

d: \(\Leftrightarrow10x-15-20x+28=19-2x^2-4x-2\)

\(\Leftrightarrow-10x+13+2x^2+4x-17=0\)

\(\Leftrightarrow2x^2-6x-4=0\)

\(\Leftrightarrow x^2-3x-2=0\)

\(\text{Δ}=\left(-3\right)^2-4\cdot1\cdot\left(-2\right)=9+8=17>0\)

Do đó: Phương trình có hai nghiệm phân biệt là:

\(\left\{{}\begin{matrix}x_1=\dfrac{3-\sqrt{17}}{2}\\x_2=\dfrac{3+\sqrt{17}}{2}\end{matrix}\right.\)

Gọi a,b,c,... cho dễ nhé!

a,\(7+2x=22-3x\)

\(\Leftrightarrow2x+3x=22-7\)

\(\Leftrightarrow5x=15\)

\(\Leftrightarrow x=3\)

Vậy...

b,\(x-12+4x=25+2x-1\)

\(\Leftrightarrow x+4x-2x=25-1+12\)

\(\Leftrightarrow3x=36\)

\(\Leftrightarrow x=12\)

Vậy...

c,\(7-\left(2x+4\right)=-\left(x+4\right)\)

\(\Leftrightarrow7-2x-4=-x-4\)

\(\Leftrightarrow-2x+x=-4+4-7\)

\(\Leftrightarrow-x=-7\)

\(\Leftrightarrow x=7\)

Vậy...

d,\(8x-3=5x+12\)

\(\Leftrightarrow8x-5x=12+3\)

\(\Leftrightarrow3x=15\)

\(\Leftrightarrow x=5\)

Vậy...

e,\(x+2x+3x-19=3x+5\)

\(\Leftrightarrow x+2x+3x-3x=5+19\)

\(\Leftrightarrow3x=24\)

\(\Leftrightarrow x=8\)

Vậy...

f,\(\left(x-1\right)-\left(2x-1\right)=9-x\)

\(\Leftrightarrow x-1-2x+1=9-x\)

\(\Leftrightarrow x-2x+x=9-1+1\)

\(\Leftrightarrow0x=9\) (Vô lý)

Vậy...

a, \(7+2x=22-3x\)

\(\Rightarrow7+2x-22+3x=0\)

\(\Rightarrow5x-15=0\)

\(\Rightarrow5x=15\Rightarrow x=3\)

b, \(x-12+4x=25+2x-1\)

\(\Rightarrow3x-12-24-2x=0\)

\(\Rightarrow x-36=0\Rightarrow x=36\)

c, \(7-\left(2x+4\right)=-\left(x+4\right)\)

\(\Rightarrow7-2x-4=-x-4\)

\(\Rightarrow3-2x+x+4=0\)

\(\Rightarrow-x=-7\Rightarrow x=7\)

d, \(8x-3=5x+12\)

\(\Rightarrow8x-3-5x-12=0\)

\(\Rightarrow3x-15=0\)

\(\Rightarrow3x=15\Rightarrow x=5\)

e, \(x+2x+3x-19=3x+5\)

\(\Rightarrow6x-19-3x-5=0\)

\(\Rightarrow3x-24=0\)

\(\Rightarrow3x=24\Rightarrow x=8\)

f, \(\left(x-1\right)-\left(2x-1\right)=9-x\)

\(\Rightarrow x-1-2x+1-9+x=0\)

(hình như câu này bị sai đề rồi, bạn xem lại đề nhé)

Chúc bạn học tốt!

a ) 10 x X - 1 - 3 - 5 - 7 - ... - 19 = 2 + 4 + 6 + ... + 20

10 x X - 1 - 3 - 5 - 7 - ... - 19 = 110

10 x X - ( 1 + 3 + 5 + 7 + ... + 19 ) = 110

10 x X - 100 = 110

10 x X = 110 + 100

10 x X = 210

       X = 210 : 10

       X = 21

a 10 x X-1-3-5-7-....-19 = 2+4+6+....+20

​10xX-1-3-5-7-....-19=110

​10xX=110+1+3+5+7+....+19

​10xX=210

​X=210:10

​X=21

b là 4

​

​

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​

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\(a,-5x\left(x-3\right)\left(2x+4\right)-\left(x+3\right)\left(x-3\right)+\left(5x-2\right)\left(3x+4\right)\)

\(=-5x\left(2x^2-x-12\right)-\left(x^2-9\right)+15x^2+20x-6x-8\)

\(=-10x^3+5x^2+60x-x^2+9+15x^2+20x-6x-8\)

\(=-10x^3+19x^2+74x+1\)

\(b,\left(4x-1\right)x\left(3x+1\right)-5x^2.x\left(x-3\right)-\left(x-4\right)x\left(x-5\right)\)\(-7\left(x^3-2x^2+x-1\right)\)

\(=\left(4x^2-x\right)\left(3x+1\right)-5x^4-15x^3-\left(x^2-4x\right)\left(x-5\right)\)\(-7x^3+14x^2-7x+7\)

\(=12x^3+x^2-x-5x^4-15x^3-x^3+9x^2+20x\)\(-7x^3+14x^2-7x+7\)

\(=-5x^4-11x^3+24x^2+12x+7\)

\(c,\left(5x-7\right)\left(x-9\right)-\left(3-x\right)\left(2-5x\right)-2x\left(x-4\right)\)

\(=5x^2-52x+63-6+17x-5x^2-2x^2+8x\)

\(=-2x^2-27x+57\)

\(d,\left(5x-4\right)\left(x+5\right)-\left(x+1\right)\left(x^2-6\right)-5x+19\)

\(=5x^2+21x-20-x^3-x^2+6x+6-5x+19\)

\(=-x^3+4x^2+22x+5\)

\(e,\left(9x^2-5\right)\left(x-3\right)-3x^2\left(3x+9\right)-\left(x-5\right)\left(x+4\right)-9x^3\)

\(=9x^3-27x^2-5x+15-9x^3-27x^2-x^2+x+20-9x^3\)

\(=-9x^3-55x^2+4x+35\)

\(g,\left(x-1\right)^2-\left(x+2\right)^2\)

\(=x^2-2x+1-x^2-4x-4\)

\(=-6x-3\)

câu 1:

a) 500-(300)-190+(-210)

= 500-300-190-210

= 200 - 210 -190

=-10 - 190

=-200

b) (-3)³ .5+12.(-6)

= -27.5 -72

=-135 - 72

=-207

c) 15.(-19-4)-19.(15-4)

= 15.(-23) - 19.11

=-345 - 209

=-554

câu 2: tìm x thuộc Z

a) 3x-2=3

=> 3x=3/2

=> x=1/2

b) x chia hết cho 5 và -7<x<11

=> x thuộc {-5;0;5;10}

Câu 1: 

a) Ta có: \(500-\left(300\right)-190+\left(-210\right)\)

\(=500-300-190-210\)

\(=\left(500-300\right)-\left(190+210\right)\)

\(=200-400=-200\)

b) Ta có: \(\left(-3\right)^3\cdot5+12\cdot\left(-6\right)\)

\(=\left(-3\right)^3\cdot5-3\cdot4\cdot3\cdot2\)

\(=-5\cdot3^3-3^2\cdot8\)

\(=3^2\cdot\left(-5\cdot3-8\right)\)

\(=9\cdot\left(-15-8\right)=9\cdot\left(-23\right)=-207\)

c) Ta có: \(15\cdot\left(-19-4\right)-19\cdot\left(15-4\right)\)

\(=-15\cdot19-15\cdot4-15\cdot19+19\cdot4\)

\(=-30\cdot19+4\cdot4\)

\(=-2\cdot\left(15\cdot19+2\cdot4\right)\)

\(=-2\cdot\left(285+8\right)=-586\)