Question

Tìm x biết

a) A= 5x²- 6x +1

b) B=x² +y²+ 2xy+ 4x+ 4y+10

Answer 1

Nếu A = 5x² - 6x + 1 = 0 (thì mình làm đc chứ đề kai sai nhé)

Ta có : 5x² - 6x + 1

= 5x² - 5x - x + 1

= (5x² - 5x) - (x - 1)

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

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

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

\(\Leftrightarrow\orbr{\begin{cases}\left(x-1\right)=0\\\left(5x-1\right)=0\end{cases}}\)

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

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