a) 16x² - ( x² + 4 )²

= ( 4x )² - ( x² + 4 )²

= [ 4x - ( x² + 4 ) ][ 4x + ( x² + 4 ) ]

= ( -x² + 4x - 4 )( x² + 4x + 4 )

= [ -( x² - 4x + 4 ) ]( x + 2 )²

= [ -( x - 2 )² ]( x + 2 )²

b) ( x + y )³ + ( x - y )³

= [ ( x + y ) + ( x - y ) ][ ( x + y )² - ( x + y )( x - y ) + ( x - y )² ]

= ( x + y + x - y )[ x² + 2xy + y² - ( x² - y² ) + x² - 2xy + y² ]

= 2x( 2x² + 2y² - x² + y²

= 2x( x² + 3y² )

1. \(\left(x+1\right)^3-125\)

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

\(=\left(x+1-5\right).\left[\left(x+1\right)^2+\left(x+1\right).5+5^2\right]\)

2. \(\left(x+4\right)^3-64\)

\(=\left(x+4\right)^3-4^3\)

\(=\left(x+4-4\right).\left[\left(x+4\right)^2+\left(x+4\right).4+4^2\right]\)

3. \(x^3-\left(y-1\right)^3\)

\(=(x^3-y+1).\left[\left(x^2\right)+x.\left(y+1\right)+\left(y+1\right)^2\right]\)

\(\)4. \(\left(a+b\right)^3-c^3\)

\(=\left[\left(a+b\right)-c\right].\left[\left(a+b\right)^2+\left(a+b\right).c+c^2\right]\)

5. \(125-\left(x+2\right)^3\)

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

\(=\left(5-x-2\right).\left[5^2+5.\left(x+2\right)+\left(x+2\right)^2\right]\)

6. \(\left(x+1\right)^3+\left(x-2\right)^3\)

\(=\left[\left(x+1\right)+\left(x-2\right)\right].\left[\left(x+1\right)^2-\left(x+1\right).\left(x-2\right)+\left(x-2\right)^2\right]\)

1)\(8x^6-\frac{1}{125}y^3=\left(2x^2\right)^3-\left(\frac{1}{5}y\right)^3\)

Bạn tự lm tiếp.AD HĐT số (7)

2)\(\left(x+4\right)^3-64=\left(x+4\right)^3-4^3\)

AD HĐT số (7).Tự lm tiếp

3)\(x^6+1=\left(x^2\right)^3+1\)

AD HĐT số (7).Tự lm tiếp

4)\(x^9+1=\left(x^3\right)^3+1\)

AD HĐT số (7).Tự lm tiếp

5,\(x^{12}-y^4=\left(x^6\right)^2-\left(y^2\right)^2\)

AD HĐT số (3).Tự lm tiếp

6)\(x^3+6x^2+12x+8=\left(x+2\right)^3\)

AD HĐT số (4)

7)\(x^3-15x^2+75x-125=\left(x-5\right)^3\)

AD HĐT số (5)

8)\(27a^3-54a^2b+36ab^2-8b^3\)

\(=\left(3a\right)^3-3.\left(3a\right)^2.2b+3.3a.\left(2b\right)^2-\left(2b\right)^3\)

\(=\left(3a-2b\right)^3\)

AD HĐT số (5)

a) 4(x²-y²)-8(x-ay)-4(a²-1)

    => 4x²-4y²-8x+8ay-4a²+4

    => 4(x²-y²-2x+2ay-a²+1)

c) a⁵+a⁴+a³ +a² +a+1

    => a(a⁴+a³+a²+a+1)+1

Đúng hết mà?

1. \(B=\left(x-2\right)\left(x+2\right)\left(x+3\right)-\left(x+1\right)^3\)

\(=\left(x^2-4\right)\left(x+3\right)-\left(x^3+3x^2+3x+1\right)\)

\(=x^3+3x^2-4x-12-x^3-3x^2-3x-1\)

\(=-7x-13\)

2. \(64-x^2-y^2+2xy=64-\left(x^2+y^2-2xy\right)\)

\(=64-\left(x-y\right)^2=\left(8+x-y\right)\left(8-x+y\right)\)

3. \(2x^3-x^2+2x-1=0\)

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

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

Vì \(x^2\ge0\)\(\Rightarrow x^2+1>0\)

\(\Rightarrow2x-1=0\)\(\Rightarrow2x=1\)\(\Rightarrow x=\frac{1}{2}\)

Vậy \(x=\frac{1}{2}\)

Bài 1.

B = ( x - 2 )( x + 2 )( x + 3 ) - ( x + 1 )³

= ( x² - 4 )( x + 3 ) - ( x³ + 3x² + 3x + 1 )

= x³ + 3x² - 4x - 12 - x³ - 3x² - 3x - 1

= -7x - 13

Bài 2.

64 - x² - y² + 2xy

= 64 - ( x² - 2xy + y² )

= 8² - ( x - y )²

= ( 8 -  x + y )( 8 + x - y )

Bài 3.

2x³ - x² + 2x - 1 = 0

<=> ( 2x³ - x² ) + ( 2x - 1 ) = 0

<=> x²( 2x - 1 ) + 1( 2x - 1 ) = 0

<=> ( 2x - 1 )( x² + 1 ) = 0

<=> \(\orbr{\begin{cases}2x-1=0\\x^2+1=0\end{cases}}\Leftrightarrow x=\frac{1}{2}\)( vì x² + 1 ≥ 1 > 0  ∀ x )

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

\(B=\left(x^2-4\right)\left(x+3\right)-\left(x^3+3x^2+3x+1\right)\)

\(B=x^2+3x^2-4x-12-x^3-3x^2-3x-1\)

\(B=-7x-13\)

2) \(64-x^2-y^2+2xy\)

\(=64-\left(x^2-2xy+y^2\right)\)

\(=64-\left(x-y\right)^2\)

\(=\left(8-x+y\right)\left(8+x-y\right)\)

3) \(2x^3-x^2+2x-1=0\)

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

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

\(\Leftrightarrow2x-1=0\Leftrightarrow x=\frac{1}{2}\)

a: \(P=-3x^3+5x\)

\(=x\cdot\left(-3x^2\right)+x\cdot5\)

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

b: \(Q=\left(2x-1\right)+\left(x-2\right)\left(2x-1\right)\)

\(=\left(2x-1\right)\left(1+x-2\right)\)

\(=\left(2x-1\right)\left(x-1\right)\)

c: \(R=4-16x^2\)

\(=4\cdot1-4\cdot4x^2\)

\(=4\left(1-4x^2\right)\)

\(=4\left(1-2x\right)\left(1+2x\right)\)

d: \(S=36-4x^2\)

\(=4\cdot9-4\cdot x^2\)

\(=4\left(9-x^2\right)\)

\(=4\left(3-x\right)\left(3+x\right)\)

e: \(T=8x^3-1\)

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

\(=\left(2x-1\right)\left(4x^2+2x+1\right)\)

f: \(Q=8-x^3\)

\(=2^3-x^3\)

\(=\left(2-x\right)\left(4+2x+x^2\right)\)

g: \(N=64-x^3\)

\(=4^3-x^3\)

\(=\left(4-x\right)\left(16+4x+x^2\right)\)