\(\left(5x+3\right)-\left(x-1\right)=4\\ 5x+3-x+1=4\\ \left(5x-x\right)+\left(3+1\right)=4\\ 4x+4=4\\ \Rightarrow4x=0\\ \Rightarrow x=0\)

\(5x^2-20\\ =5\left(x^2-4\right)\\ =5\left(x-2\right)\left(x+2\right)\)

\(x^2-20x+100-4y^2\\ =\left(x-10\right)^2-\left(2y\right)^2\\ =\left(x-10-2y\right)\left(x-10+2y\right)\)

\(3x^2y\left(2x^2-y\right)-4x^2\left(x^2y-y^2\right)\\ =6x^4y-3x^2y^2-4x^4y+4x^2y^2\\ =\left(-3x^2y^2+4x^2y^2\right)+\left(6x^4y-4x^4y\right)\\ =2x^4y+x^2y^2\)

Ác-hen-ti-na còn có lý

tưởng D mà  Phnôm-Pênh , cu-ba đúng mà

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

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

\(3x^2-12xy+12y^2\)

\(=3(x^2-4xy+4y^2)\)

\(=3[x^2-4xy+(2y)^2] \)

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

\((x-1)^2-4\)

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

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

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

\(=x(x-3)+1(x-3)\)

\(=(x+1)(x-3)\)