Question

Tìm x,y biết:

a) (2x+3).(x-2) -( x² -4x + 4) = 0

b) 9x² -( x² - 4x +4) =0

Answer 1

Lời giải:

a) $(2x+3)(x-2)-(x^2-4x+4)=0$

$\Leftrightarrow (2x+3)(x-2)-(x-2)^2=0$

$\Leftrightarrow (x-2)[(2x+3)-(x-2)]=0$

$\Leftrightarrow (x-2)(x+1)=0$

$\Rightarrow x-2=0$ hoặc $x+1=0$

$\Rightarrow x=2$ hoặc $x=-1$

b)

$9x^2-(x^2-4x+4)=0$

$\Leftrightarrow (3x)^2-(x-2)^2=0$

$\Leftrightarrow (3x-x+2)(3x+x-2)=0$

$\Leftrightarrow (2x+2)(4x-2)=0$

$\Leftrightarrow (x+1)(2x-1)=0$

$\Rightarrow x+1=0$ hoặc $2x-1=0$

$\Rightarrow x=-1$ hoặc $x=\frac{1}{2}$