Question

x² + 6x - 7 = 0 Tìm x

Answer 1

<=>\(\left(x-1\right)\left(x+7\right)=0\)

<=>\(\left[{}\begin{matrix}x-1=0\\x+7=0\end{matrix}\right.\)

<=>\(\left[{}\begin{matrix}x=1\\x=-7\end{matrix}\right.\)

Answer 2

<=> x^2+6x+9-16

<=>(x+3)^2-4^2=0

<=>( x+3-4).(x+3+4)=0

<=>x-1=0

x+7=0

<=>x=1 hoặc x=-7