a.x^3-1^3

b.x^3-5^3

c)(2x)^3+3^3

d)x^3+1/2^3

1. (x - 1)^3 + 3.(x - 3)^2 - (x + 2).(x^2 - 2x + 4) = (x + 2)^3 - (x - 3).(x^2 + 9) - 6x^2 + 5 
<=> x^3 - 3x^2 + 3x - 1 + 3(x^2 - 6x + 9) - (x^3 + 2^3) 
= x^3 + 6x^2 + 12x + 8 - (x^3 - 3x^2 + 9x -27) - 6x^2 + 5 
<=> x^3 - 3x^2 + 3x - 1 + 3x^2 - 18x + 27 - x^3 - 8 
= x^3 + 6x^2 + 12x + 8 - x^3 + 3x^2 - 9x + 27 - 6x^2 + 5 
<=> 3x - 18x -12x - 3x^2 + 9x = 27 + 5 + 8 + 8 + 1 - 27 
<=> - 3x^2 - 18x - 22 = 0 
<=> 3x^2 + 18x + 22 = 0 

Nửa chu vi mảnh đất là: 

                                               120 : 2 = 60 (m)

Chiều dài hơn chiều rộng là:

                                               5 + 5 = 10 (m)

Chiều rộng là:

                                          ( 60 - 10 ) : 2 = 25 (m)

Chiều dài là:

                                                25 + 10 = 35 (m)

Diện tích là:

                                               25  35 = 875 ( )

1,2,3,4 không tính được.

`5)(2x-1/2)^2`

`=(2x)^2-2+(1/2)^2`

`=4x^2-2+1/4`

`6)(x+1/4)^2`

`=x^2+1/2x+1/16`

3) \(3x-2y^2=\left(\sqrt{3x}\right)^2-\left(y\sqrt{2}\right)^2=\left(\sqrt{3x}-y\sqrt{2}\right)\left(\sqrt{3x}+y\sqrt{2}\right)\)

4) \(5x-y^2=\left(\sqrt{5x}-y\right)\left(\sqrt{5x}+y\right)\)

b: \(\Leftrightarrow2\left(x^2-2x+1\right)-3x^2+5x-1=0\)

\(\Leftrightarrow2x^2-4x+2-3x^2+5x-1=0\)

\(\Leftrightarrow-x^2+x+1=0\)

\(\Leftrightarrow x^2-x-1=0\)

\(\text{Δ}=\left(-1\right)^2-4\cdot1\cdot\left(-1\right)=5\)

Vì Δ>0 nên phương trình có hai nghiệm phân biệt là:

\(\left\{{}\begin{matrix}x_1=\dfrac{1-\sqrt{5}}{2}\\x_2=\dfrac{1+\sqrt{5}}{2}\end{matrix}\right.\)

c: \(\Leftrightarrow x^2+6x+9-1-\left(x^2+8x-4x-32\right)=0\)

\(\Leftrightarrow x^2+6x+8-x^2-4x+32=0\)

=>2x+40=0

hay x=-20

d: \(\Leftrightarrow3x^2+12x+12+4x^2-4x+1-7\left(x^2-9\right)=36\)

\(\Leftrightarrow7x^2+8x+13-7x^2+63=36\)

=>8x+76=36

hay x=-5

B)(5-3x)^2=25+9x^2-30x

c)(5-x^2)(5+x^2)=25-x^4

d)(5x-1)^3=125x^3-1+15x-75x^2

e)(x^2+3)(x^4+9-3x^2)=x^6+27

f)( x-4y)(x^2+4 xy+16 y^2)= x^3-64 y^3

a) \(\left(5x-2\right)^2-\left(7-6x\right)^2=0\)

\(\Leftrightarrow\left(5x-2-7+6x\right)\left(5x-2+7-6x\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}11x-9=0\\-x+5=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=\frac{9}{11}\\x=5\end{cases}}}\)

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

\(\Leftrightarrow9x^2+6x+1+25x^2+20x+4=x+5\)

\(\Leftrightarrow34x^2+26x+5=x+5\)

\(\Leftrightarrow34x^2+25x=0\)

\(\Leftrightarrow x\left(34x+25\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x=0\\34x+25=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=0\\x=\frac{-25}{34}\end{cases}}}\)

c) Tự làm nốt

a) ( 5x - 2 )² - ( 7 - 6x )² = 0

<=> [ 5x - 2 - ( 7 - 6x ) ][ 5x - 2 + ( 7 - 6x ) ] = 0

<=> [ 5x - 2 - 7 + 6x ][ 5x - 2 + 7 - 6x ] = 0

<=> [ 11x - 9 ][ 5 - x ] = 0

<=> \(\orbr{\begin{cases}11x-9=0\\5-x=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{9}{11}\\x=5\end{cases}}\)

b) ( 3x - 1 )² + ( 5x + 2 )² = x + 5 

<=> 9x² - 6x + 1 + 25x² + 20x + 4 = x + 5

<=> 34x² + 14x + 5 = x + 5

<=> 34x² + 14x + 5 - x - 5 = 0

<=> 34x² + 13x = 0

<=> 13x( 34/13x + 1 ) = 0

<=> \(\orbr{\begin{cases}13x=0\\\frac{34}{13}x+1=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=0\\x=-\frac{13}{34}\end{cases}}\)

c) ( x - 2 )² - ( 3 + 2x )² = 20x - 4 

<=> x² - 4x + 4 - ( 4x² + 12x + 9 ) = 20x - 4

<=> x² - 4x + 4 - 4x² - 12x - 9 - 20x + 4 = 0

<=> -3x² - 36x - 1 = 0

=> Vô nghiệm ( bấm EQN ra nghiệm vô tỉ )

a, \(\left(5x-2\right)^2-\left(7-6x\right)^2=0\)

\(\Leftrightarrow25x^2-20x+4-49+84x-36x^2=0\)

\(\Leftrightarrow-11x^2+64x-45=0\)

\(\Leftrightarrow x\left(11x-9\right)-5\left(11x-9\right)=0\)

\(\Leftrightarrow\left(x-5\right)\left(11x-9\right)=0\Leftrightarrow\orbr{\begin{cases}x=5\\x=\frac{9}{11}\end{cases}}\)

a ) ( 2x + 1 )² - 4 ( x + 2 )² = 9

   4x² + 4x + 1 - 4 ( x² +4x + 4 ) = 9

   4x² + 4x + 1 - 4x² -16x -16      = 9

            -12x - 15                         = 9

            -12x                                = 24

                x                                 = -2

b) 3 ( x - 1 )² - 3x ( x - 5 ) = 1

    3 ( x² - 2x + 1 ) - 3x² + 15x = 1

    3x² - 6x + 3 - 3x² + 15x      = 1

             9x + 3                        = 1

             9x                              = -2

              x                               = \(\frac{-2}{9}\)                         

Bài bao nhiêu