Question

Tìm x biết:

a) 5x(x-1)=x-1

b) 2(x+5)-x²-5x=0

Answer 1

a) \(5x\left(x-1\right)=x-1\)

\(\Rightarrow5x\left(x-1\right)-\left(x-1\right)=0\)

\(\Rightarrow\left(x-1\right).\left(5x-1\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x-1=0\\5x-1=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=1\\x=\frac{1}{5}\end{cases}}\)

Vậy \(x=1\) hoặc \(x=\frac{1}{5}\)

b) \(2\left(x+5\right)-x^2-5x\)

\(\Rightarrow2\left(x+5\right)-x\left(x+5\right)\)

\(\Rightarrow\left(x+5\right).\left(2-x\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x+5=0\\2-x=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=-5\\x=2\end{cases}}\)

Vậy \(x=-5\)hoặc \(x=2\)