Question

tìm x biết: (x+2)^2 + (x-3) - 2(x-1)(x+1)=9

Answer 1

\(\Leftrightarrow x^2+4x+4+x-3-2\left(x^2-1\right)=9.\)

\(\Leftrightarrow-x^2+5x-6=0\)

\(\Leftrightarrow x^2-5x+6=0\Leftrightarrow x^2-2x-3x+6=0\Leftrightarrow x\left(x-2\right)-3\left(x-2\right)=0\)

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

\(\Leftrightarrow\orbr{\begin{cases}x_1=2\\x_2=3\end{cases}}\)