\(a,\left(x-2\right)^2-\left(x-3\right)\left(x^2+3x+9\right)+6\left(x+1\right)^2=15\)\(\Leftrightarrow x^3-6x^2+12x-8-x^3+27+6\left(x^2+2x+1\right)=15\)\(\Leftrightarrow-6x^2+12x+19+6x^2+12x+6=15\)

\(\Leftrightarrow24x=-10\)

\(\Leftrightarrow x=-\dfrac{5}{12}\)

Vậy:....

\(b,\left(5x+1\right)^2-\left(5x+3\right)\left(5x-3\right)=30\)

\(\Leftrightarrow25x^2+10x+1-25^2+9=30\)

\(\Leftrightarrow10x=20\)

\(\Rightarrow x=2\)

Vậy :....

\(c,\left(x+3\right)\left(x^2-3x+9\right)-x\left(x-2\right)\left(x+2\right)=15\)\(\Leftrightarrow x^3+27-x\left(x^2-4\right)=15\)

\(\Leftrightarrow x^3+27-x^3+4x=15\)

\(\Leftrightarrow4x=15-27=-12\)

\(\Leftrightarrow x=-3\)

vậy : .....

$ (3x-1)(2x+7)-(x+1)(6x-5)=16 $

$ 6x^2+21x-2x-7-(6x^2+x-5)=16 $

$ 25x-7-x+5=16 $

$ 24x-2=16 $

$ 24x=18 $

$ x=\frac{3}{4} $

$ (10x+9)x-(5x-1)(2x+3)=8 $

$ 10x^2+9x-(10x^2+13x-3)=8 $

$ 10x^2+9x-10x^2-13x+3=8 $

$ -4x+3=8 $

$ -4x=5 $

$ x=-\frac{5}{4} $

a)  ( 3x - 1 ) ( 2x + 7 )  - ( x + 1 ) ( 6x + 5 ) = 16 

<=> 6x² + 21x - 2x - 7 - ( 6x² - 5x + 6x - 5) = 16

<=> 6x² + 21x - 2x - 7 - ( 6x² + x - 5 )        = 16 

<=> 6x²+ 21x - 2x - 7 - 6x² -x + 5              = 16 

<=> 18x - 2                                             = 16 

<=>  18x                                                 = 18 

=>        x                                                 = 1

Vậy....  

a)

$(3x-1)(2x+7)-(x+1)(6x-5)=16$

$6x^2+19x-7-(6x^2+x-5)=16$

$18x-2=16$

$18x=18$

x = 1

b)

$(10x+9)x-(5x-1)(2x+3)=8$

$10x^2+9x-(10x^2+13x-3)=8$

$-4x+3=8$

$-4x=5$

x= -5/4

c) Hiểu đề là $(3x-5)(7-5x)+(5x+2)(2x+3)-2=0$.

$(3x-5)(7-5x)+(5x+2)(2x+3)-2=0$

$-15x^2+46x-35+10x^2+19x+6-2=0$

$-5x^2+65x-31=0$

$5x^2-65x+31=0$

$x=\frac{65\pm\sqrt{3605}}{10}$

d)

$x(x+1)(x+6)-x^3=5x$

$x(x^2+7x+6)-x^3=5x$

$x^3+7x^2+6x-x^3=5x$

$7x^2+x=0$

$x(7x+1)=0$

=> x = 0 hoặc x = -1/7

a) ( 5x + 1 )² - ( 5x + 3 )( 5x - 3 ) = 30

⇔ 25x² + 10x + 1 - ( 25x² - 9 ) = 30

⇔ 25x² + 10x + 1 - 25x² + 9 = 30

⇔ 10x + 10 = 30

⇔ 10x = 20

⇔ x = 2

b) ( x + 3 )² + ( x - 2 )( x + 2 ) - 2( x - 1 )² = 7

⇔ x² + 6x + 9 + x² - 4 - 2( x² - 2x + 1 ) = 7

⇔ 2x² + 6x + 5 - 2x² + 4x - 2 = 7

⇔ 10x + 3 = 7

⇔ 10x = 4

⇔ x = 4/10 = 2/5

a. (3x - 1).(2x + 7) - (x + 1).(6x - 5) = 16
<=> 6x^2 + 19x - 7 - (6x^2 + x - 5) = 16
<=> 18x - 2 = 16
<=> 18x = 18
<=> x = 1
b. (10x + 9).x - (5x - 1).(2x + 3) = 8
<=> 10x^2 + 9x - (10x^2 + 13x - 3) = 8
<=> -4x + 3 = 8
<=> -4x = 5
<=> x = -5/4
c. (3x - 5).(7 - 5x) + (5x + 2).(3x - 2) - 2 = 0
<=> -15x^2 + 46x - 35 + 15x^2 - 4x - 4 - 2 = 0
<=> 42x - 41 = 0
<=> x = 41/42

a) (3x - 1)(2x + 7) - (x + 1)(6x - 5) = 16

6x² + 21x - 2x - 7 - 6x² + 5x - 6x + 5 = 16

(6x² - 6x²) + (21x - 2x + 5x - 6x) + (-7 + 5) = 16

18x - 2 = 16

18x = 18

x = 1

Vậy x = 1

b) (10x + 9)x - (5x - 1)(2x + 3) = 8

10x² + 9x - 10x² - 15x + 2x + 3 = 8

(10x² - 10x²) + (9x - 15x + 2x) + 3 = 8

-4x + 3 = 8

-4x = 5

x = \(\frac{-5}{4}\)

Vậy x = \(\frac{-5}{4}\)

c) x(x + 1)(x + 6) - x³ = 5x

(x² + x)(x + 6) - x³ = 5x

x³ + 7x² + 6x - x³ = 5x

7x² + 6x = 5x

x(7x + 6) = 5x

=> 7x + 6 = 5

7x = -1

x = \(\frac{-1}{7}\)

Vậy x = \(\frac{-1}{7}\)

d) (3x - 5)(7 - 5x) + (5x + 2)(3x - 2) - 2 = 0

21x - 15x² - 35 + 25x + 15x² - 10x + 6x - 4 - 2 = 0

(-15x² + 15x²) + (21x + 25x - 10x + 6x) + (-35 - 4 - 2) = 0

42x - 41 = 0

42x = 41

x = \(\frac{41}{42}\)

Vậy x = \(\frac{41}{42}\)

a/ \(\left(x+2\right)^2-9=0\)

<=> \(\left(x+2-3\right)\left(x+2+3\right)=0\)

<=> \(\left(x-1\right)\left(x+5\right)=0\)

<=> \(\orbr{\begin{cases}x-1=0\\x+5=0\end{cases}}\)

<=> \(\orbr{\begin{cases}x=1\\x=-5\end{cases}}\)

b/ \(x^2-2x+1=25\)

<=> \(\left(x-1\right)^2=25\)

<=> \(\orbr{\begin{cases}x-1=5\\x-1=-5\end{cases}}\)

<=> \(\orbr{\begin{cases}x=6\\x=-4\end{cases}}\)

a) (x+2)²=0

 ==> x+2=0

 ==> x=0-2

==> x=-2

309 do