Question

1)

a) \(x^2\)+6x +9 ; b) 10x - 25 - \(x^2\)

c) 8\(x^3\) -\(\dfrac{1}{8}\) ; d) \(\dfrac{1}{25}\)\(x^2\) - 64\(y^2\)

Answer 1

Câu a :

\(x^2+6x+9=\left(x+3\right)^2\)

Câu b :

\(10x-25-x^2=-\left(x^2-10x+25\right)=-\left(x-5\right)^2\)

Câu c :

\(8x^3-\dfrac{1}{8}=\left(2x\right)^3-\left(\dfrac{1}{2}\right)^3\) \(=\left(2x-\dfrac{1}{2}\right)\left[\left(2x\right)^2+\dfrac{1}{2}.2x+\left(\dfrac{1}{2}\right)^2\right]\)

Cau d :

\(\dfrac{1}{25}x^2-64y^2=\left(\dfrac{1}{5}\right)^2-\left(8y\right)^2=\left(\dfrac{1}{5}+8\right)\left(\dfrac{1}{5}-8\right)\)