a) (2x² - x) + 4x - 2 = 0

x(2x - 1) + 2(2x - 1) = 0

(2x - 1)(x + 2) = 0

2x - 1 = 0 hoặc x + 2 = 0

* 2x - 1 = 0

2x = 1

x = \(\frac{1}{2}\)

* x + 2 = 0

x = -2

Vậy x = -2; x = \(\frac{1}{2}\)

b) x² - 6x + 8 = 0

x² - 2x - 4x + 8 = 0

(x² - 2x) + (-4x + 8) = 0

x(x - 2) - 4(x - 2) = 0

(x - 2)(x - 4) = 0

x - 2 = 0 hoặc x - 4 = 0

* x - 2 = 0

x = 2

* x - 4 = 0

x = 4

Vậy x = 2; x = 4

c) x⁴ - 8x² - 9 = 0

x⁴ + x² - 9x² - 9 = 0

(x⁴ - 9x²) + (x² - 9) = 0

x²(x² - 9) + (x² - 9) = 0

(x² - 9)(x² + 1) = 0

x² - 9 = 0 (vì x² + 1 > 0 với mọi x)

x² = 9

x = 3 hoặc x = -3

Vậy x = 3; x = -3

15 - 2x = 11

=> 2x = 15 - 11

=> 2x = 4

=> x = 4 : 2 = 2

3.(x - 9) + 15 = 81

=> 3x - 27 = 81 - 15

=> 3x - 27 = 66

=> 3x = 66 + 27

=> 3x = 93

=> x = 93 : 3 = 31

a) 15 - 2.x = 11

           2.x = 4

              x = 2

b) 3. (x - 9) + 15 = 81

    3. (x - 9)         = 66

         x - 9          = 22

         x               = 31

c) (x+1)+(x+2)+...+(x+10)= 105

    (x+x+....+x) + (1+2+....+10) = 105

     x . 10 + 55 = 105

     x . 10         = 50

     x                = 5 

a, 15 - 2x = 11

=> 2x = 4

=> x = 2

vay_

b, 3(x - 9) + 15 = 81

=> 3(x - 9) = 66

=> x - 9 = 22

=> x = 31

vay_

c, (x + 1) + (x + 2) + (x + 3) + ... + (x + 10) = 105

=> x + 1 + x + 2 + x + 3 + ... + x + 10 = 105

=> (x + x + x + ... + x) + (1 + 2 + 3 + ... + 10) = 105

=> 10x + 55 = 105

=> 10x = 50

=> x = 5

vay_

Anh cj giúp e vs ạ

Venus is the 2 nd planet in the Solar System , with the most similar mass and size to Earth . This planet has no life, the gravity of Venus is 8.87 m/s² . The average surface temperature is 735 K (462 °C)  , so Venus is the hottest planet in the solar system . I just know that

(x-3)(x²+3x+9)+x(5-x²)=6x

x(x²+3x+9)-3(x²+3x+9)+x(5-x²)=6x

x³+3x²+9x-3x²-9x-27+5x-x³-6x=0

(x³-x³)+(3x²-3x²)+(9x-9x+5x-6x)=27

-x=27

x=-27