Toán Lớp 8: Tìm x, biết:
a) x.(x+1)-x.(x-3)=8
b)x^2-6x+8=0
c)2x^2+2x+1/2=0
Giúp mình nha
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Toán Lớp 8: Tìm x, biết:
a) x.(x+1)-x.(x-3)=8
b)x^2-6x+8=0
c)2x^2+2x+1/2=0
Giúp mình nha
Comments ( 2 )
$⇔x^2+x-x^2+3x=8$
$⇔x=2$
Vậy $x=2$
$⇔x^2-4x-2x+8=0$
$⇔x(x-4)-2(x-4)=0$
$⇔(x-2)(x-4)=0$
$⇔\left[\begin{matrix}x-2=0\\x-4=0\end{matrix}\right.$
$⇔\left[\begin{matrix}x=2\\x=4\end{matrix}\right.$
Vậy S={2;4}
$⇔2(x^2+x+\dfrac{1}{4})=0$
$⇔2(x+\dfrac{1}{2})^2=0$
$⇔x+\dfrac{1}{2}=0$
$⇔x=\dfrac{-1}{2}$
Vậy S={\frac{-1}{2}}