Question

* Tìm x:     3x(2x-4)-(6x-1)(x+2)=25

* Rút gọn phân thức: ( x^2 - 2xy + y^2 )(x-y) - (x-y)(x^2 + xy + y^2)

 

 

Answer 1

a) Ta có: \(3x\left(2x-4\right)-\left(6x-1\right)\left(x+2\right)=25\)

\(\Rightarrow6x^2-12x-\left(6x^2+12x-x-2\right)=25\)

\(\Rightarrow6x^2-12x-6x^2-12x+x+2=25\)

\(\Rightarrow-23x+2=25\)

\(\Rightarrow-23x=25-2-23\)

\(\Rightarrow x=23:\left(-23\right)=-1\)

Vậy x = -1

b) \(\left(x^2-2xy+y^2\right)\left(x-y\right)-\left(x-y\right)\left(x^2+2xy+y^2\right)\)

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

\(=\left(x-y\right)2x^2\)