Question

ko làm tắt

Answer 1

Answer 2

Bài 4: 

a) Ta có: \(x^2-3x=0\)

\(\Leftrightarrow x\left(x-3\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=3\end{matrix}\right.\)

c) Ta có: \(4x^3-x=0\)

\(\Leftrightarrow x\left(2x-1\right)\left(2x+1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{1}{2}\\x=-\dfrac{1}{2}\end{matrix}\right.\)

Answer 3

Bài 3: 

c) Ta có: \(C=xy\left(x+y\right)-2x-2y\)

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

\(=7\cdot\left(8-2\right)=7\cdot6=42\)