Question

[Trịnh Ngọc Bảo Long]

giup voi et o et

Answer 1

[Yen Nhi]

`Answer:`

a) \(3x+15=0\)

\(\Leftrightarrow3x=-15\)

\(\Leftrightarrow x=-5\)

b) \(2\left(x-3\right)=x+4\)

\(\Leftrightarrow2x-6=x+4\)

\(\Leftrightarrow2x-x=4+6\)

\(\Leftrightarrow x=10\)

c) \(x^2-9=\left(2x-1\right)\left(x+3\right)\)

\(\Leftrightarrow\left(x-3\right)\left(x+3\right)=\left(2x-1\right)\left(x+3\right)\)

\(\Leftrightarrow\left(x-3\right)\left(x+3\right)-\left(2x-1\right)\left(x+3\right)=0\)

\(\Leftrightarrow\left(x+3\right)\left(x-3-2x+1\right)=0\)

\(\Leftrightarrow\left(x+3\right)\left(-x-2\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x+3=0\\-x-2=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=-3\\-x=2\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=-3\\x=-2\end{cases}}}\)

d) \(\frac{x+2}{x-2}-\frac{1}{x}=\frac{2}{x^2-2x}\left(ĐK:x\ne0;x\ne2\right)\)

\(\Leftrightarrow\frac{x\left(x+2\right)}{x\left(x-2\right)}-\frac{x-2}{x\left(x-2\right)}=\frac{2}{x\left(x-2\right)}\)

\(\Rightarrow x\left(x+2\right)-x+2=2\)

\(\Leftrightarrow x^2+2x-x+2-2=0\)

\(\Leftrightarrow x^2+x=0\)

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

\(\Leftrightarrow\orbr{\begin{cases}x=0\\x+1=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=0\text{(Loại)}\\x=-1\end{cases}}}\)