2(x-5)-3(x+7)=14

=> 2x-10-3x-21=14

=> x(2-3)-31=14

=> -x=14+31

=> -x=45

=> x=-45

45 - ( x + 45 - 3 ) = l -7 + 3 l

45 - x - 45 + 3 = 4

45 - x - 45 = 4 - 3

45 - x - 45 = 1

45 - x = 1 + 45

45 - x = 46

=> x = 45 - 46

=> x = -1

Vậy x = -1

\(45-x-45+3=|-4|^{ }_{ }_{ }\)\(|^{ }_{ }\)

\(3-x=4\)

\(x=-1\)

45 - x - 45 + 3 = |-7+3| => -x + 3 = |-4| => -x + 3 = 4 => -x = 1 => x = -1

(8x−3)(3x+2)−(4x+7)(x+4)=(2x+1)(5x−1)(8x−3)(3x+2)−(4x+7)(x+4)=(2x+1)(5x−1)

 20x2−16x−34=10x2+3x−120x2−16x−34=10x2+3x−1

 10x2−19x−33=010x2−19x−33=0

 (10x+11)(x−3)=0

chỉ bt lm con b thoy

..army,,,,,,,,,,

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

\(\Leftrightarrow3x^2-12x-2=3x^2-17x+20\)

\(\Leftrightarrow3x^2-12x=3x^2-17x+20+2\)

\(\Leftrightarrow3x^2-12x=3x^2-17x+22\left(3x^2-17x\right)\)

\(\Leftrightarrow5x=22\)

\(\Rightarrow x=\frac{22}{5}\)

b) \(\left(8x-3\right)\left(3x+2\right)-\left(4x+7\right)\left(x+4\right)=\left(2x+1\right)\left(5x-1\right)\)

\(\Leftrightarrow20x^2-16x-34=10x^2+3x+1\)

\(\Leftrightarrow20x^2-16x-33=10x^2+3x\)

\(\Leftrightarrow20x^2-16x-33=10x^2+3x-3x\)

\(\Leftrightarrow20x^2-16x-33=10x^2\)

\(\Leftrightarrow20x^2-16x-33=10x^2-10x^2\)

\(\Leftrightarrow20x^2-16x-33=0\)

\(\Rightarrow\orbr{\begin{cases}x=3\\x=-\frac{11}{10}\end{cases}}\)

a, ( 2x + 3 )(x - 4) + ( x - 5 )( x - 2) =( 3x - 5 ) ( x - 4 )
<-> 2x² - 8x + 3x - 12 + x² - 2x - 5x + 10 = 3x² - 12x - 5x + 20
<-> 3x² - 10x - 2 = 3x² - 15x + 20
<-> 3x² - 3x² - 10x + 15x = 20 + 2
<-> 5x = 22
<-> x = 22/5

a, 5/2 + 3/4 : x = -1/2

=> x = -1/4

b, 1/2 . x + 3/5 . x = -2/3

=> x = -20/33

c, 4/7 . x - x = -9/14

=> x = 3/2

a, (x + 2) + (x + 4) + (x + 6) + ... + (x + 50) = 750

=> x + 2 + x + 4 + x + 6 + ... + x + 50 = 750

=> (x + x + x + ... + x) + (2 + 4 + 6 + ... + 50) = 750

=> 25x + (50 + 2).25 : 2 = 750

=> 25x + 52.25 : 2 = 750

=> 25x + 650 = 750

=> 25x = 100

=> x = 4

a) ( x+x+...+x)+(2+4+6+...+50)= 750

     ( x*25)+ (50+2)*25:2 = 750

      (x*25)+ 650              = 750

         x* 25                      = 750 - 650 = 100

         x                             = 100 :25 = 4

Bài 1: 

1 - 2  + 3 - 4 + .... + 2009 - 2010

= (1 - 2) + (3 - 4) + ... + (2009 - 2010)

= -1 .  1005

= -1005

Bài 2:

a) (15 - x) - (-x + 12) = 7 - (-5 + x)

=> 15 - x + x - 12 = 7 + 5 - x

=> -x + x + x = 7 + 5 - 15 + 12

=> x = 9

b) (x - 5)⁴ = (x - 5)⁶

=> x - 5 = 1 hoặc x - 5 = 0

=> x = 6 hoặc x = 5

c) (x + 1) + (x + 3) + ... + (x + 99) = 0

=> (x . 50) + (1 + 3 + ... + 99) = 0

=> (x . 50) + 2500 = 0

=> x . 50 = -2500

=> x = -50

Ta có : 1 - 2 + 3 - 4 + ..... + 2009 - 2010 

= (1 - 2) + (3 - 4) + ..... + (2009 - 2010)

= -1 + (-1) + ..... + (-1)

= -1.1005

= -1005

\(\frac{7^{x+2}+7^{x+1}+7^x}{57}=\frac{5^{2x}+5^{2x+1}+5^{2x+3}}{131}\)

<=>\(\frac{7^x\left(7^2+7+1\right)}{57}=\frac{5^{2x}.\left(1+5+5^3\right)}{131}\)

<=>\(\frac{7^x.57}{57}=\frac{5^{2x}.131}{131}\)

<=>\(7^x=5^{2x}\)<=>\(7^x=10^x\)<=>x=0

Vậy x=0