Câu sai : góc A = góc B

a) (x-1)(x+1)(x+2)          

=\(\left(x^2-1\right)\) (x+2) 

= \(x^3+2x^2-x-2\)

TL:

a) (x-1) (x+2)

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

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

(2x-3)² - 2(2x-3)(2 - x) + (x-2)² 

= (2x-3)² - (2x-3)(2 - x) - (2x-3)(2 - x ) - (2 - x)²

= (2x-3)(3x - 5) - (2-x)(3x - 5)

= (3x - 5)²

Ui mình sai.

Sửa : 

(2x-3)² - (2x-3)(2-x) + (x-2)²

= (2x-3)² - (2x-3)(2-x) + (2-x)²

= (3x-5)(2x-3) + (3x-5)(2-x)

= (3x-5)(x -1)

13) \(x^2-4xy-25+4y^2=\left(x+2y\right)^2-25=\left(x+2y+5\right)\left(x+2y-5\right)\)

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

19) \(x^3-8y^3=\left(x-2y\right)\left(x^2+2xy+4y^2\right)\)

18) \(36x^2-y^2+12x+1=\left(6x+1\right)^2-y^2=\left(6x-y+1\right)\left(6x+y+1\right)\)

17) \(4x\left(2x-1\right)-2x^2\left(1-2x\right)=4x\left(2x-1\right)+2x^2\left(2x-1\right)=2x\left(2x-1\right)\left(x+2\right)\)

16) \(x^3-x^2y-xy^2+y^3=x^2\left(x-y\right)-y^2\left(x-y\right)=\left(x-y\right)^2\left(x+y\right)\)

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

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

 Đề bài là s ; t ko hiểu ; m viết lại đi , yêu cầu đề là gì 

Đắp án : \(\left(x-1\right)^3\)

Lời giải chi tiết ( có thể là do bạn vt sai đầu bài ) 

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

\(=x^3-3.x^2.1-3.x.1-1\)

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