Câu a : \(x^2-6x+8\)
\(=x^2-2x-4x+8\)
\(=x\left(x-2\right)-4\left(x-2\right)\)
\(=\left(x-2\right)\left(x-4\right)\)
Câu b : \(x^2\left(x-3\right)+12-4x\)
\(=x^2\left(x-3\right)+4\left(3-x\right)\)
\(=x^2\left(x-3\right)-4\left(x-3\right)\)
\(=\left(x-3\right)\left(x^2-4\right)\)
\(=\left(x-3\right)\left(x-2\right)\left(x+2\right)\)
Câu c : \(x^3-\dfrac{1}{4}x\)
\(=x\left(x^2-\dfrac{1}{4}\right)\)
\(=x\left(x-\dfrac{1}{2}\right)\left(x+\dfrac{1}{2}\right)\)
Câu d : \(\left(x+2\right)^2-x^2+4\)
\(=\left(x+2\right)^2-\left(x^2-4\right)\)
\(=\left(x+2\right)^2-\left(x+2\right)\left(x-2\right)\)
\(=\left(x+2\right)\left(x+2-x+2\right)\)
\(=4\left(x+2\right)\)
a, Ta có: x2 - 6x + 8
= x2 - 6x +9 -1
= ( x2 - 2*3x + 32)-1
= (x-3)2 -1
= (x-3-1) * (x-3+1)
b, x2 (x-3)+ 12 - 4x
= x2(x-3)+4(3-x)
= x2(x-3)-4(x-3)
=(x2-4)(x-3)
=(x-2)(x+2)(x-3)
c,x3-1/4x
=x(x2-1/4)
=x(x-1/2)(x+1/2)
d,(x+2)2-x2+4
=x2+4x+4-x2+4
=4x+8
=4(x+2)
