Question

Tính

a. (x-y) (2x + 3y)

b. (4x²-4x+1)=(2x-1)

C. x+1/x-1 - x-1/x+1 - 4/x^2

Answer 1

a) (x-y)(2x+3y)=2x²+3xy-2xy+3y²=2x²+xy+3y²

b) (2x-1)²-(2x-1)=0

<=> 2x-1=0 <=> x=\(\dfrac{1}{2}\)

 

Answer 2

a) Ta có: (x-y)(2x+3y)

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

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

Answer 3

b) Ta có: \(4x^2-4x+1=2x-1\)

\(\Leftrightarrow4x^2-4x+1-2x+1=0\)

\(\Leftrightarrow4x^2-4x-2x+2=0\)

\(\Leftrightarrow4x\left(x-1\right)-2\left(x-1\right)=0\)

\(\Leftrightarrow\left(x-1\right)\left(4x-2\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\4x-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=\dfrac{1}{2}\end{matrix}\right.\)

Vậy: \(x\in\left\{1;\dfrac{1}{2}\right\}\)