Question

tìm x biết 

a) (6x-3) (2x+4) + (4x-1) (5-3x) = -21

b) 6x (3x+5) - 2x (9x-2) + (17-x) (x-1) + x (x-18) =0

c) (15-2x) (4x+1) - (13-4x) (2x-3) - (x-1) (x+2) + x²=52

d) (8x-3) (3x+2) - (4x+7) (x+4) = (2x+1) (5x-1) - 33

Answer 1

Rút gọn hết ta được :

a/ 41x - 17 = -21

=> 41x = -4 => x = 4/41

b/ 34x - 17 = 0 

=> 34x = 17

=> x = 17/34 = 1/2

c/ 19x + 56 = 52 

=> 19x = -4

=> x = -4/19

d/ 20x² - 16x - 34 = 10x² + 3x - 34

=> 10x² - 19x = 0

=> x(10x - 19) = 0

=> x = 0 

hoặc 10x - 19 = 0 => 10x = 19 => x = 19/10

Vậy x = 0 ; x = 19/10

Answer 2

Rút gọn hết ta được :

a/ 41x - 17 = -21

=> 41x = -4 => x = 4/41

b/ 34x - 17 = 0

=> 34x = 17

=> x = 17/34 = 1/2

c/ 19x + 56 = 52

=> 19x = -4

=> x = -4/19

d/ 20x 2 - 16x - 34 = 10x 2 + 3x - 34

=> 10x 2 - 19x = 0

=> x(10x - 19) = 0

=> x = 0 hoặc 10x - 19 = 0

=> 10x = 19

=> x = 19/10

Vậy x = 0 ; x = 19/10 

Answer 3

a) ( 6x - 3 ) ( 2x + 4 ) + ( 4x - 1 ) ( 5 - 3x ) = -21

<=> 12x² + 24x - 6x - 12 + 20x - 12x² - 5 + 3x = -21

<=> 41x = -21 + 12 + 5 

<=> 41x = -4

<=> x = -4/41

Answer 4

a) ( 6x - 3 )( 2x + 4 ) + ( 4x - 1 )( 5 - 3x ) = -21

<=> 12x² + 18x - 12 + 23x - 12x² - 5 = -21

<=> 41x - 17 = -21

<=> 41x = -4

<=> -4/41

b) 6x( 3x + 5 ) - 2x( 9x - 2 ) + ( 17 - x )( x - 1 ) + x( x - 18 ) = 0

<=> 18x² + 30x - 18x² + 4x + 17x - 17 - x² + x + x² - 18x = 0

<=> 34x - 17 = 0

<=> 34x = 17

<=> x = 17/34 = 1/2

c) ( 15 - 2x )( 4x + 1 ) - ( 13 - 4x )( 2x - 3 ) - ( x - 1 )( x + 2 ) + x² = 52

<=> -8x² + 58x + 15 - ( -8x² + 38x - 39 ) - ( x² + x - 2 ) + x² = 52

<=> -8x² + 58x + 15 + 8x² - 38x + 39 - x² - x + 2 + x² = 52

<=> 19x + 56 = 52

<=> 19x = -4

<=> x = -4/19

d) ( 8x - 3 )( 3x + 2 ) - ( 4x + 7 )( x + 4 ) = ( 2x + 1 )( 5x - 1 ) - 33

<=> 24x² + 7x - 6 - ( 4x² + 23x + 28 ) = 10x² + 3x - 1 - 33

<=> 24x² + 7x - 6 - 4x² - 23x - 28 = 10x² + 3x - 34

<=> 20x² - 16x - 34 = 10x² + 3x - 34

<=> 20x² - 16x - 34 - 10x² - 3x + 34 = 0

<=> 10x² - 19x = 0

<=> x( 10x - 19 ) = 0

<=> x = 0 hoặc 10x - 19 = 0

<=> x = 0 hoặc x = 19/10

Answer 5

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