a) Ta có: \(8x^2+30x+7\)

\(=8x^2+28x+2x+7\)

\(=4x\left(2x+7\right)+\left(2x+7\right)\)

\(=\left(2x+7\right)\left(4x+1\right)\)

b) Ta có: \(4x^3-12x^2+9x\)

\(=x\left(4x^2-12x+9\right)\)

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

c) Ta có: \(\left(2x+1\right)^2-\left(x-1\right)^2\)

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

\(=\left(x+2\right)\cdot3x\)

d) Ta có: \(ab+c^2-ac-bc\)

\(=\left(ab-bc\right)+\left(c^2-ac\right)\)

\(=b\left(a-c\right)+c\left(c-a\right)\)

\(=b\left(a-c\right)-c\left(a-c\right)\)

\(=\left(a-c\right)\left(b-c\right)\)

e) Ta có: \(4x^2-y^2+1-4x\)

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

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

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

f) Ta có: \(6x^2-7x-20\)

\(=6x^2-15x+8x-20\)

\(=3x\left(2x-5\right)+4\left(2x-5\right)\)

\(=\left(2x-5\right)\left(3x+4\right)\)

\(4x^3-12x^2+9x=x\left(4x^2-12x+9\right)=x\left(2x-3\right)^2\), \(\left(2x+1\right)^2-\left(x-1\right)^2=\left(2x+1-x+1\right)\left(2x+1+x-1\right)=\left(x+2\right)3x\)

\(ab+c^2-ac-bc=ab-ac-bc+c^2=a\left(b-c\right)-c\left(b-c\right)=\left(b-c\right)\left(a-c\right)\)

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

\(6x^2-7x-20=6x^2-15x+8x-20=3x\left(2x-5\right)+4\left(2x-5\right)=\left(2x-5\right)\left(3x+4\right)\)

\(8x^2+30x+7=8x^2+2x+28x+7=2x\left(4x+1\right)+7\left(4x+1\right)=\left(4x+1\right)\left(2x+7\right)\)

\(2x-1^3+8\)

\(=2x-9\)

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

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

_________

\(8x^3-12x^2+6x-1\)

\(=\left(2x\right)^3-3\cdot\left(2x\right)^2\cdot1+3\cdot2x\cdot1^2-1^3\)

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

_______________

\(8x^3-12x^2+6x-2\)

\(=8x^3-12x^2+6x-1-1\)

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

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

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

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

________

\(9x^3-12x^2+6x-1\)

\(=x^3+8x^3-12x^2+6x-1\)

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

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

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

b: 8x^3-12x^2+6x-1

=(2x)^3-3*(2x)^2*1+3*2x*1^2-1^3

=(2x-1)^3

c: =(8x^3-12x^2+6x-1)-1

=(2x-1)^3-1

=(2x-1-1)[(2x-1)^2+2x-1+1]

=2(x-1)(4x^2-4x+1+2x)

=2(x-1)(4x^2-2x+1)

8x³ - 12x² + 6x - 1

= (2x)³ - 3.(2x)².1 + 3.2x.1 - 1³

= (2x - 1)³

--------------------

8x³ - 12x² + 6x - 2

= 8x³ - 12x² + 6x - 1 - 1

= (2x)³ - 3.(2x)².1 + 3.(2x).1 - 1³ - 1³

= (2x - 1)³ - 1³

= (2x - 1 - 1)[(2x - 1)² + (2x - 1).1 + 1]

= (2x - 2)(4x² - 4x + 1 + 2x - 1 + 1)

= 2(x - 1)(4x² - 2x + 1)

--------------------

9x³ - 12x² + 6x - 1

= x³ + 8x³ - 12x² + 6x - 1

= x³ + (2x)³ - 3.(2x)² + 3.2x.1² - 1³

= x³ + (2x - 1)³

= (x + 2x - 1)[x² - x.(2x - 1) + (2x - 1)²]

= (3x - 1)(x² - 2x² + x + 4x² - 4x + 1)

= (3x - 1)(3x² - 3x + 1)

Rút gọn nha các cậu

\(A=\left(\frac{6x+1}{x^2-6x}+\frac{6x-1}{x^2+6x}\right)\times\frac{x^2-36}{12x^2+12}\)

\(A=\left[\frac{6x+1}{x\left(x-6\right)}+\frac{6x-1}{x\left(x+6\right)}\right]\times\frac{\left(x+6\right)\left(x-6\right)}{12\left(x^2+1\right)}\)

\(A=\frac{6x^2+36x+x+6+6x^2-36x-x+6}{x}\times\frac{1}{12\left(x^2+1\right)}\)

\(A=\frac{12\left(x^2+1\right)}{x}\times\frac{1}{12\left(x^2+1\right)}=\frac{1}{x}\)

`(6x+1)^2-2(1+6x)(6x-1)+(6x-1)^2`

`=(6x+1-6x+1)^2`

`=2^2=4`