Question

[Hoàng Ngọc Diệp Chi]

Mọi người giúp vs, mik đang cần gấp!

Answer 1

[2611]

     `(x + 1)(x - 3 ) - x^2 = 2 ( x - 2 )`

`<=>x^2 - 3x + x - 3 - x^2 = 2x - 4`

`<=> x^2 - x^2 - 3x + x - 2x = - 4 + 3`

`<=> -4x = -1`

`<=> x = 1 / 4`

Vậy `S = { 1 / 4 }`

Answer 2

[Nguyễn Ngọc Huy Toàn]

a.\(\left(x+1\right)\left(x-3\right)-x^2=2\left(x-2\right)\)

\(\Leftrightarrow x^2-3x+x-3-x^2=2x-4\)

\(\Leftrightarrow-4x=-1\)

\(\Leftrightarrow x=\dfrac{1}{4}\)

b.\(\dfrac{3}{x+3}+\dfrac{x}{x-3}=1\) ;\(ĐK:x\ne\pm3\)

\(\Leftrightarrow\dfrac{3\left(x-3\right)+x\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}=\dfrac{\left(x-3\right)\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}\)

\(\Leftrightarrow3\left(x-3\right)+x\left(x+3\right)=\left(x-3\right)\left(x+3\right)\)

\(\Leftrightarrow3x-9+x^2+3x=x^2-9\)

\(\Leftrightarrow6x=0\)

\(\Leftrightarrow x=0\left(tm\right)\)

c.\(\left|x+7\right|=3x+1\)

\(\Leftrightarrow\left[{}\begin{matrix}x+7=3x+1;x\ge-7\\-x-7=3x+1;x< 7\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=3\left(tm\right)\\x=-2\left(tm\right)\end{matrix}\right.\)