Question

[Bảo Ngô]

tìm x biết 

x² -8x+9=0

Answer 1

[%Hz@]

\(x^2-8x+9=0\)\(\Rightarrow x^2-9x+x+9=0\)\(\Rightarrow x^2+x-9x+9=0\)\(\Rightarrow x\left(x+1\right)-9\left(x+1\right)=0\)\(\Rightarrow\left(x+1\right)\left(x-9\right)=0\)\(\Rightarrow\orbr{\begin{cases}x+1=0\\x-9=0\end{cases}\Rightarrow\orbr{\begin{cases}x=-1\\x=9\end{cases}}}\)Có j sai thông cẻm :>>

Answer 2

[khang]

x2-8x+9= x2-9x+x+9=x(x+1)-9(x+1)=(x+1)(x-9) x+1=0=>x=-1 hoặc x-9=0=>x=9