=8x^2+12x=4x(2x+3)

\(x^2+7x^2+12x=8x^2+12x=4x\left(2x+3\right)\)

\(=\left(x+2\right)\left(x+5\right)\)

\(x^2+7x+10=\left(x^2+5x\right)+\left(2x+10\right)=x\left(x+5\right)+2\left(x+5\right)=\left(x+2\right)\left(x+5\right)\)

\(x=-10\) hoặc \(x=3\)

\(\Leftrightarrow x^2+10x-3x-30=0\\ \Leftrightarrow x\left(x+10\right)-3\left(x+10\right)=0\\ \Leftrightarrow\left(x+10\right)\left(x-3\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=-10\\x=3\end{matrix}\right.\)

x³ - 7x² + 10x

=x³ - 2x² - 5x² + 10x

=(x³ -2x²) - (5x² - 10x)

= x²( x - 2) - 5x( x - 2)

= (x - 2) (x² - 5x)

Gõ trên máy tính nên hơi lâu 

Cảm ơn mình đê

x²-7x+12

=x²-4x-3x+12

=x(x-4)-3(x-4)

=(x-3)(x-4)

        \(x^2-7x+12\)

\(=\left(x^2-4x\right)-\left(3x-12\right)\)

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

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

C

(x^2+3x+2)(x^2+7x+12)

=(x²+x+2x+2)(x²+3x+4x+12)

=[x.(x+1)+2.(x+1)][x.(x+3)+4.(x+3)]

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