Question

x^2-2x-3=0




Giúp với ạ=)

 

Answer 1

`x^{2}-2x-3=0`

`<=>(x^{2}+x)-(3x+3)=0`

`<=>x(x+1)-3(x+1)=0`

`<=>(x+1)(x-3)=0`

`=>x+1=0` hoặc `x-3=0`

`<=>x=-1` hoặc `x=3`

Vậy `S={-1;3}`

Answer 2

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

\(\Leftrightarrow\left(x-3\right)\left(x+1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x-3=0\\x+1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-1\end{matrix}\right.\)

Vậy \(S=\left\{3;-1\right\}\)

Answer 3

`x^2 - 2x - 3 = 0`

`=> ( x^2 + x ) + ( -3x - 3 ) = 0`

`=> x . ( x + 1 ) - 3 . ( x + 1 ) = 0`

`=> ( x + 1 ) . ( x - 3 ) = 0`

`=> x+1 = 0` hoặc `x-3=0`

`=> x=-1` hoặc `x=3`

   Vậy `x in { -1; 3 }`