Question

tìm x biết : a) 5x(x-1)=x-1

                b) 2 ( x+5) - x²-5x=0

Answer 1

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

=> 5.(x - 1) - (x - 1) = 0

=> (x - 1).(5 - 1) = 0

=> (x - 1).4 = 0

=> x - 1 = 0

=> x = 0 + 1 = 1

b) 2.(x + 5) - x² - 5x = 0

=> 2.(x + 5) - x.(x + 5) = 0

=> (x + 5).(2 - x) = 0

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

Answer 2

a) 5x(x-1) = x-1 

5x = 1

x= 1/5

b) 2(x+5) - x^2 - 5x =0

2(x+5) -x(x+5) = 0

(2-x) (x+5) =0

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

Vậy x=2 hoặc x=-5