Tìm x biết x^2-2x-3=0 x^2+3x+2=0 Làm sai report 09/09/2021 Bởi Abigail Tìm x biết x^2-2x-3=0 x^2+3x+2=0 Làm sai report
` x^2 – 2x -3 =0` `<=> x^2 + x – 3x – 3=0` `<=> x(x+1) – 3(x+1) =0` `<=> (x-3)(x+1) =0` `<=>` \(\left[ \begin{array}{l}x-3=0\\x+1=0\end{array} \right.\) `⇔` \(\left[ \begin{array}{l}x=3\\x=-1\end{array} \right.\) Vậy `S = {-1;3}` . `x^2 + 3x +2 =0` `<=> x^2 + x + 2x + 2 =0` `<=> x(x+1) + 2(x+1)=0` `<=> (x+2)(x+1) =0` `<=>` \(\left[ \begin{array}{l}x+2=0\\x+1=0\end{array} \right.\) `<=>` \(\left[ \begin{array}{l}x=-2\\x=-1\end{array} \right.\) Vậy `S = {-2;-1}` Bình luận
Đáp án: `x²-2x-3=0` `⇔x²+x-3x-3=0` `⇔x(x+1)-3(x+1)=0` `⇔(x-3)(x+1)=0` `S={3;-1}` `x²+3x+2=0` `x²+2x+x+2=0` `⇔x(x+2)+(x+2)=0` `⇔(x+2)(x+1)=0` `S={-2;-1}` Giải thích các bước giải: Bình luận
` x^2 – 2x -3 =0`
`<=> x^2 + x – 3x – 3=0`
`<=> x(x+1) – 3(x+1) =0`
`<=> (x-3)(x+1) =0`
`<=>` \(\left[ \begin{array}{l}x-3=0\\x+1=0\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x=3\\x=-1\end{array} \right.\)
Vậy `S = {-1;3}`
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`x^2 + 3x +2 =0`
`<=> x^2 + x + 2x + 2 =0`
`<=> x(x+1) + 2(x+1)=0`
`<=> (x+2)(x+1) =0`
`<=>` \(\left[ \begin{array}{l}x+2=0\\x+1=0\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x=-2\\x=-1\end{array} \right.\)
Vậy `S = {-2;-1}`
Đáp án:
`x²-2x-3=0`
`⇔x²+x-3x-3=0`
`⇔x(x+1)-3(x+1)=0`
`⇔(x-3)(x+1)=0`
`S={3;-1}`
`x²+3x+2=0`
`x²+2x+x+2=0`
`⇔x(x+2)+(x+2)=0`
`⇔(x+2)(x+1)=0`
`S={-2;-1}`
Giải thích các bước giải: